Provided by: nghttp2-proxy_1.40.0-1ubuntu0.3_amd64 bug

NAME

       nghttpx - HTTP/2 proxy

SYNOPSIS

       nghttpx [OPTIONS]... [<PRIVATE_KEY> <CERT>]

DESCRIPTION

       A reverse proxy for HTTP/2, and HTTP/1.

       <PRIVATE_KEY>
              Set   path  to  server's private  key.   Required  unless "no-tls" parameter is used in --frontend
              option.

       <CERT> Set  path   to   server's   certificate.    Required   unless  "no-tls"   parameter  is   used  in
              --frontend option.   To make OCSP stapling work, this must be an absolute path.

OPTIONS

       The options are categorized into several groups.

   Connections
       -b, --backend=(<HOST>,<PORT>|unix:<PATH>)[;[<PATTERN>[:...]][[;<PARAM>]...]
              Set  backend  host  and   port.   The  multiple  backend addresses are  accepted by repeating this
              option.  UNIX domain socket  can be   specified  by  prefixing   path  name  with  "unix:"  (e.g.,
              unix:/var/run/backend.sock).

              Optionally,  if <PATTERN>s are given, the backend address is  only  used  if  request matches  the
              pattern.   The pattern  matching is  closely  designed  to ServeMux  in net/http  package  of   Go
              programming  language.   <PATTERN>  consists  of  path, host +  path or just host.   The path must
              start  with "/".  If  it ends with "/",  it matches all  request path  in  its subtree.   To  deal
              with   the request  to the  directory without  trailing slash,  the path which ends  with "/" also
              matches  the request path which  only  lacks  trailing  '/'  (e.g.,  path  "/foo/" matches request
              path   "/foo").  If it does  not end with "/", it  performs exact match against  the request path.
              If  host  is given,  it  performs  a match  against  the request host.   For a   request  received
              on   the  frontend  listener  with   "sni-fwd"  parameter  enabled, SNI  host is used instead of a
              request host.  If host alone is given, "/" is  appended to it,  so that it  matches   all  request
              paths   under  the   host   (e.g., specifying  "nghttp2.org" equals  to "nghttp2.org/").   CONNECT
              method  is treated specially.  It  does not have  path,  and  we   don't  allow  empty  path.   To
              workaround  this, we assume that CONNECT method has "/" as path.

              Patterns  with   host take  precedence over  patterns with just path.   Then, longer patterns take
              precedence over shorter ones.

              Host  can  include "*"  in  the  left most  position  to indicate  wildcard  match   (only  suffix
              match  is   done).   The  "*"  must  match  at  least one character.  For example, host    pattern
              "*.nghttp2.org"    matches    against "www.nghttp2.org"  and   "git.ngttp2.org",  but   does   not
              match   against  "nghttp2.org".   The exact  hosts  match takes precedence over the wildcard hosts
              match.

              If path  part ends with  "*", it is treated   as  wildcard  path.   The   wildcard  path   behaves
              differently   from  the  normal path.  For normal path,  match is made around the boundary of path
              component  separator,"/".  On the other hand, the wildcard  path does not take  into  account  the
              path  component   separator.   All  paths which  include the wildcard  path  without  last  "*" as
              prefix,  and  are strictly longer than wildcard  path without last "*"  are  matched.   "*"   must
              match   at  least  one   character.   For example,  the   pattern  "/foo*"  matches   "/foo/"  and
              "/foobar".  But it does not match "/foo", or "/fo".

              If <PATTERN> is omitted or  empty string, "/" is used as pattern,   which   matches   all  request
              paths  (catch-all pattern).  The catch-all backend must be given.

              When doing  a match, nghttpx made  some normalization to pattern, request host and path.  For host
              part, they are converted to lower case.  For  path  part,  percent-encoded  unreserved  characters
              defined  in  RFC  3986   are  decoded,  and  any   dot-segments (".."  and ".")   are resolved and
              removed.

              For   example,   -b'127.0.0.1,8080;nghttp2.org/httpbin/' matches the  request  host  "nghttp2.org"
              and   the  request  path "/httpbin/get", but does not match the request host "nghttp2.org" and the
              request path "/index.html".

              The  multiple  <PATTERN>s   can   be  specified,   delimiting  them             by            ":".
              Specifying  -b'127.0.0.1,8080;nghttp2.org:www.nghttp2.org'   has   the  same   effect   to specify
              -b'127.0.0.1,8080;nghttp2.org' and -b'127.0.0.1,8080;www.nghttp2.org'.

              The backend addresses sharing same <PATTERN> are grouped together forming  load balancing  group.

              Several parameters <PARAM> are accepted after <PATTERN>.  The  parameters are  delimited  by  ";".
              The    available   parameters         are:       "proto=<PROTO>",        "tls",  "sni=<SNI_HOST>",
              "fall=<N>",          "rise=<N>",    "affinity=<METHOD>",       "dns",       "redirect-if-not-tls",
              "upgrade-scheme",                                "mruby=<PATH>",        "read-timeout=<DURATION>",
              "write-timeout=<DURATION>",  "group=<GROUP>",    "group-weight=<N>",   and    "weight=<N>".    The
              parameter  consists   of  keyword,  and  optionally followed by  "=" and value.  For  example, the
              parameter "proto=h2"  consists of  the keyword  "proto" and   value  "h2".   The  parameter  "tls"
              consists of the keyword "tls" without value.  Each parameter is described as follows.

              The  backend application protocol  can be specified using optional  "proto"   parameter,  and   in
              the   form  of "proto=<PROTO>".  <PROTO> should be one of the  following  list   without   quotes:
              "h2",  "http/1.1".    The  default value of <PROTO> is  "http/1.1".  Note that usually "h2" refers
              to HTTP/2  over TLS.  But in this  option, it may mean HTTP/2  over cleartext  TCP  unless   "tls"
              keyword is used (see below).

              TLS   can    be   enabled   by   specifying    optional   "tls"  parameter.  TLS is not enabled by
              default.

              With "sni=<SNI_HOST>"  parameter,  it  can  override  the  TLS  SNI   field   value   with   given
              <SNI_HOST>.   This  will default to the backend <HOST> name

              The   feature   to  detect  whether  backend  is online  or offline can be enabled  using optional
              "fall" and "rise" parameters.   Using  "fall=<N>"  parameter,  if  nghttpx cannot  connect   to  a
              this  backend  <N>   times  in   a  row,  this  backend  is  assumed  to be  offline,  and  it  is
              excluded from load balancing.  If <N> is 0, this backend never  be excluded  from load   balancing
              whatever   times  nghttpx  cannot  connect   to  it,  and  this   is  the default.  There is  also
              "rise=<N>" parameter.  After  backend was excluded from load balancing group, nghttpx periodically
              attempts  to make a connection to the failed backend, and if the  connection is made  successfully
              <N> times  in a row, the backend is assumed to  be online,  and  it  is  now  eligible   for  load
              balancing  target.    If  <N>   is  0,  a backend  is permanently  offline, once  it goes  in that
              state, and this is the default behaviour.

              The     session     affinity    is      enabled      using  "affinity=<METHOD>"   parameter.    If
              "ip" is  given  in <METHOD>, client  IP based session affinity  is enabled.  If "cookie"  is given
              in <METHOD>,  cookie based session affinity is   enabled.   If   "none"  is  given   in  <METHOD>,
              session  affinity   is  disabled, and this  is the default.  The session  affinity is  enabled per
              <PATTERN>.   If at least  one backend  has   "affinity"   parameter,  and   its  <METHOD>  is  not
              "none",   session affinity is enabled for all backend  servers sharing the same  <PATTERN>.  It is
              advised  to  set  "affinity" parameter  to   all   backend  explicitly  if  session  affinity   is
              desired.   The  session  affinity  may   break  if   one  of  the   backend  gets unreachable,  or
              backend  settings  are   reloaded  or replaced by API.

              If    "affinity=cookie"     is    used,     the     additional   configuration                  is
              required.  "affinity-cookie-name=<NAME>" must be  used to specify a name     of     cookie      to
              use.      Optionally, "affinity-cookie-path=<PATH>" can   be  used  to   specify  a  path    which
              cookie    is   applied.    The   optional "affinity-cookie-secure=<SECURE>"  controls  the  Secure
              attribute of a cookie.  The default value is "auto", and the Secure attribute is  determined by  a
              request  scheme.  If a request scheme is "https", then Secure attribute is set.  Otherwise, it  is
              not set.  If  <SECURE> is "yes", the  Secure attribute  is  always set.   If  <SECURE>   is  "no",
              the Secure attribute is always omitted.

              By  default,  name  resolution  of  backend  host  name  is  done  at   start   up,   or reloading
              configuration.   If  "dns" parameter   is  given,   name  resolution   takes   place  dynamically.
              This  is  useful   if backend address changes frequently.   If  "dns"  is given,  name  resolution
              of backend   host   name   at  start   up,   or   reloading configuration is skipped.

              If "redirect-if-not-tls" parameter  is  used,  the  matched  backend   requires    that   frontend
              connection    is   TLS  encrypted.   If it isn't, nghttpx responds to the request with 308  status
              code, and  https URI the  client should use instead  is included in Location  header  field.   The
              port  number in  redirect URI is 443 by  default, and can be  changed using  --redirect-https-port
              option.   If at least one  backend has  "redirect-if-not-tls" parameter, this feature  is  enabled
              for  all  backend  servers  sharing  the    same    <PATTERN>.     It     is    advised   to   set
              "redirect-if-no-tls"    parameter   to    all   backends explicitly if this feature is desired.

              If "upgrade-scheme"  parameter is used along  with "tls" parameter, HTTP/2 :scheme  pseudo  header
              field  is  changed  to  "https"  from "http" when forwarding a request to this particular backend.
              This is  a workaround for a backend server  which  requires  "https" :scheme  pseudo  header field
              on TLS encrypted connection.

              "mruby=<PATH>"   parameter   specifies   a   path  to  mruby script  file  which  is  invoked when
              this  pattern  is matched.  All backends which share the same pattern must  have  the  same  mruby
              path.

              "read-timeout=<DURATION>"  and "write-timeout=<DURATION>" parameters  specify the  read and  write
              timeout  of the backend connection  when this  pattern is  matched.  All backends which share  the
              same  pattern must have the same timeouts.  If these timeouts  are entirely omitted for a pattern,
              --backend-read-timeout           and --backend-write-timeout are used.

              "group=<GROUP>"  parameter specifies  the name  of group this  backend  address  belongs  to.   By
              default,  it  belongs  to   the  unnamed   default  group.    The  name  of group  is unique   per
              pattern.   "group-weight=<N>"   parameter specifies the  weight of  the group.  The  higher weight
              gets   more  frequently   selected   by   the  load   balancing  algorithm.  <N> must be  [1, 256]
              inclusive.  The weight 8 has 4 times more weight  than 2.  <N> must be the same for  all addresses
              which   share  the   same  <GROUP>.    If "group-weight" is  omitted in an address,  but the other
              address  which  belongs  to  the  same  group   specifies  "group-weight",    its     weight    is
              used.      If    no  "group-weight"   is   specified   for  all  addresses,  the weight of a group
              becomes 1.  "group" and "group-weight" are ignored if session affinity is enabled.

              "weight=<N>"  parameter  specifies  the  weight  of  the backend  address  inside  a  group  which
              this   address  belongs   to.   The   higher   weight  gets more  frequently selected by  the load
              balancing algorithm.   <N> must be [1,  256] inclusive.   The  weight 8  has  4 times  more weight
              than  weight   2.  If  this parameter  is omitted, weight  becomes  1.   "weight"  is  ignored  if
              session affinity is enabled.

              Since ";" and ":" are  used as delimiter, <PATTERN> must not  contain  these   characters.   Since
              ";" has  special meaning in shell, the option value must be quoted.

              Default: 127.0.0.1,80

       -f, --frontend=(<HOST>,<PORT>|unix:<PATH>)[[;<PARAM>]...]
              Set   frontend   host and  port.   If  <HOST> is  '*',  it assumes  all addresses  including  both
              IPv4 and  IPv6.  UNIX domain  socket can  be specified by   prefixing  path  name   with   "unix:"
              (e.g.,   unix:/var/run/nghttpx.sock).   This   option  can  be used  multiple times  to listen  to
              multiple addresses.

              This option  can take  0 or  more parameters,  which are described  below.    Note    that   "api"
              and  "healthmon" parameters are mutually exclusive.

              Optionally, TLS  can be disabled by  specifying "no-tls" parameter.  TLS is enabled by default.

              If  "sni-fwd"  parameter  is   used, when performing a match to select a backend server,  SNI host
              name received from the client  is used  instead of  the request  host.  See --backend option about
              the pattern match.

              To   make  this   frontend  as   API endpoint,  specify "api" parameter.   This   is  disabled  by
              default.    It  is important  to  limit the  access  to  the API   frontend.   Otherwise,  someone
              may  change   the backend  server, and break your services,  or expose confidential information to
              the outside the world.

              To  make  this  frontend  as  health  monitor  endpoint, specify  "healthmon"   parameter.    This
              is   disabled   by  default.   Any  requests which come through  this address are replied with 200
              HTTP status, without no body.

              To  accept   PROXY  protocol    version   1    on   frontend  connection,   specify   "proxyproto"
              parameter.   This  is disabled by default.

              Default: *,3000

       --backlog=<N>
              Set listen backlog size.

              Default: 65536

       --backend-address-family=(auto|IPv4|IPv6)
              Specify   address  family  of  backend  connections.   If "auto" is given, both IPv4  and IPv6 are
              considered.  If "IPv4" is  given, only  IPv4 address is  considered.  If  "IPv6"  is  given,  only
              IPv6 address is considered.

              Default: auto

       --backend-http-proxy-uri=<URI>
              Specify       proxy        URI       in       the      form http://[<USER>:<PASS>@]<PROXY>:<PORT>.
              If   a   proxy requires  authentication,  specify  <USER>  and  <PASS>.  Note that  they  must  be
              properly   percent-encoded.  This proxy  is used  when the  backend connection  is HTTP/2.  First,
              make  a CONNECT  request  to  the proxy  and  it connects  to the  backend  on behalf  of nghttpx.
              This  forms   tunnel.    After   that,  nghttpx   performs  SSL/TLS handshake with  the downstream
              through  the   tunnel.   The  timeouts  when  connecting  and   making  CONNECT  request  can   be
              specified    by     --backend-read-timeout    and --backend-write-timeout options.

   Performance
       -n, --workers=<N>
              Set the number of worker threads.

              Default: 1

       --single-thread
              Run  everything  in  one   thread  inside the worker process.  This   feature   is   provided  for
              better   debugging experience,   or   for   the  platforms   which   lack   thread  support.    If
              threading  is disabled,  this  option  is always enabled.

       --read-rate=<SIZE>
              Set maximum  average read  rate on  frontend connection.  Setting 0 to this option means read rate
              is unlimited.

              Default: 0

       --read-burst=<SIZE>
              Set  maximum read  burst  size  on frontend  connection.  Setting  0  to this  option  means  read
              burst  size  is unlimited.

              Default: 0

       --write-rate=<SIZE>
              Set  maximum   average  write  rate on  frontend connection.  Setting 0 to this option means write
              rate is unlimited.

              Default: 0

       --write-burst=<SIZE>
              Set  maximum write  burst size  on frontend  connection.  Setting  0 to  this  option means  write
              burst size  is unlimited.

              Default: 0

       --worker-read-rate=<SIZE>
              Set  maximum  average  read  rate  on  frontend connection per worker.  Setting  0 to  this option
              means read  rate is unlimited.  Not implemented yet.

              Default: 0

       --worker-read-burst=<SIZE>
              Set maximum  read burst size on  frontend connection per worker.  Setting 0 to this  option  means
              read burst size is unlimited.  Not implemented yet.

              Default: 0

       --worker-write-rate=<SIZE>
              Set  maximum   average  write  rate on  frontend connection per worker.  Setting  0 to this option
              means write rate is unlimited.  Not implemented yet.

              Default: 0

       --worker-write-burst=<SIZE>
              Set maximum write burst  size on frontend connection per worker.  Setting 0 to this  option  means
              write burst size is unlimited.  Not implemented yet.

              Default: 0

       --worker-frontend-connections=<N>
              Set maximum number  of simultaneous connections frontend accepts.  Setting 0 means unlimited.

              Default: 0

       --backend-connections-per-host=<N>
              Set   maximum  number   of   backend concurrent  connections (and/or  streams in  case  of HTTP/2)
              per origin  host.  This option  is meaningful when --http2-proxy  option is  used.    The   origin
              host   is   determined   by   authority  portion  of  request URI (or :authority  header field for
              HTTP/2).   To  limit   the    number   of   connections   per  frontend         for        default
              mode,       use --backend-connections-per-frontend.

              Default: 8

       --backend-connections-per-frontend=<N>
              Set   maximum number  of  backend concurrent  connections (and/or streams  in case of HTTP/2)  per
              frontend.  This option  is   only  used  for  default   mode.   0  means unlimited.  To limit  the
              number   of   connections   per  host  with           --http2-proxy          option,           use
              --backend-connections-per-host.

              Default: 0

       --rlimit-nofile=<N>
              Set maximum number of open files (RLIMIT_NOFILE) to <N>.  If 0 is given, nghttpx does not set  the
              limit.

              Default: 0

       --backend-request-buffer=<SIZE>
              Set buffer size used to store backend request.

              Default: 16K

       --backend-response-buffer=<SIZE>
              Set buffer size used to store backend response.

              Default: 128K

       --fastopen=<N>
              Enables  "TCP Fast  Open" for  the listening  socket and limits the  maximum length for the  queue
              of connections that have not yet completed the three-way handshake.  If value is 0 then fast  open
              is disabled.

              Default: 0

       --no-kqueue
              Don't  use   kqueue.   This  option is only  applicable for the platforms  which have kqueue.  For
              other platforms, this option will be simply ignored.

   Timeout
       --frontend-http2-read-timeout=<DURATION>
              Specify read timeout for HTTP/2 frontend connection.

              Default: 3m

       --frontend-read-timeout=<DURATION>
              Specify read timeout for HTTP/1.1 frontend connection.

              Default: 1m

       --frontend-write-timeout=<DURATION>
              Specify write timeout for all frontend connections.

              Default: 30s

       --frontend-keep-alive-timeout=<DURATION>
              Specify   keep-alive   timeout   for   frontend   HTTP/1 connection.

              Default: 1m

       --stream-read-timeout=<DURATION>
              Specify  read timeout  for HTTP/2  streams.  0  means no timeout.

              Default: 0

       --stream-write-timeout=<DURATION>
              Specify write  timeout for  HTTP/2 streams.  0  means no timeout.

              Default: 1m

       --backend-read-timeout=<DURATION>
              Specify read timeout for backend connection.

              Default: 1m

       --backend-write-timeout=<DURATION>
              Specify write timeout for backend connection.

              Default: 30s

       --backend-connect-timeout=<DURATION>
              Specify  timeout before  establishing TCP  connection to backend.

              Default: 30s

       --backend-keep-alive-timeout=<DURATION>
              Specify   keep-alive   timeout    for   backend   HTTP/1 connection.

              Default: 2s

       --listener-disable-timeout=<DURATION>
              After accepting  connection failed,  connection listener is disabled  for a given  amount of time.
              Specifying 0 disables this feature.

              Default: 30s

       --frontend-http2-setting-timeout=<DURATION>
              Specify  timeout before  SETTINGS ACK  is received  from client.

              Default: 10s

       --backend-http2-settings-timeout=<DURATION>
              Specify  timeout before  SETTINGS ACK  is received  from backend server.

              Default: 10s

       --backend-max-backoff=<DURATION>
              Specify   maximum  backoff   interval.   This   is  used  when doing health  check against offline
              backend  (see "fail" parameter  in --backend  option).   It is  also used  to limit  the   maximum
              interval   to   temporarily   disable  backend   when  nghttpx   failed to  connect to  it.  These
              intervals are calculated  using exponential backoff, and consecutive failed attempts increase  the
              interval.  This option caps its maximum value.

              Default: 2m

   SSL/TLS
       --ciphers=<SUITE>
              Set  allowed   cipher  list   for  frontend  connection.  The format of the string is described in
              OpenSSL ciphers(1).  This option  sets cipher suites for  TLSv1.2 or earlier.  Use --tls13-ciphers
              for TLSv1.3.

              Default:
              ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA384:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256

       --tls13-ciphers=<SUITE>
              Set  allowed   cipher  list   for  frontend  connection.  The format of the string is described in
              OpenSSL ciphers(1).  This  option  sets   cipher    suites   for   TLSv1.3.    Use  --ciphers  for
              TLSv1.2 or earlier.

              Default: TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256

       --client-ciphers=<SUITE>
              Set   allowed  cipher   list  for   backend connection.   The format of the string is described in
              OpenSSL  ciphers(1).   This  option   sets  cipher  suites   for    TLSv1.2   or   earlier.    Use
              --tls13-client-ciphers for TLSv1.3.

              Default:
              ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA384:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256

       --tls13-client-ciphers=<SUITE>
              Set   allowed  cipher   list  for   backend connection.   The format of the string is described in
              OpenSSL   ciphers(1).    This    option    sets    cipher     suites     for     TLSv1.3.      Use
              --tls13-client-ciphers for TLSv1.2 or earlier.

              Default: TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256

       --ecdh-curves=<LIST>
              Set   supported   curve   list   for  frontend  connections.  <LIST> is a  colon separated list of
              curve  NID or names in the preference order.  The supported curves depend on the  linked   OpenSSL
              library.  This  function  requires OpenSSL >= 1.0.2.

              Default: X25519:P-256:P-384:P-521

       -k, --insecure
              Don't  verify backend  server's  certificate  if TLS  is enabled for backend connections.

       --cacert=<PATH>
              Set  path  to  trusted  CA   certificate  file.  It is used in backend  TLS connections  to verify
              peer's  certificate.   It  is  also  used  to   verify  OCSP  response  from  the  script  set  by
              --fetch-ocsp-response-file.   The   file  must  be  in  PEM  format.    It  can  contain  multiple
              certificates.  If the  linked OpenSSL  is configured  to load  system wide certificates, they  are
              loaded at startup  regardless of this option.

       --private-key-passwd-file=<PATH>
              Path   to file  that contains  password for  the server's private key.   If none is  given and the
              private  key is password protected it'll be requested interactively.

       --subcert=<KEYPATH>:<CERTPATH>[[;<PARAM>]...]
              Specify  additional certificate  and  private key  file.  nghttpx will  choose certificates  based
              on   the hostname indicated by client using TLS SNI extension.  If nghttpx is  built with  OpenSSL
              >= 1.0.2,  the shared  elliptic curves (e.g., P-256) between  client and  server  are  also  taken
              into   consideration.   This  allows  nghttpx  to send ECDSA certificate  to modern clients, while
              sending RSA based certificate to older  clients.  This option can be used  multiple   times.    To
              make  OCSP  stapling  work, <CERTPATH> must be absolute path.

              Additional parameter  can be specified in  <PARAM>.  The available <PARAM> is "sct-dir=<DIR>".

              "sct-dir=<DIR>"   specifies  the   path  to   directory  which  contains        *.sct        files
              for         TLS  signed_certificate_timestamp  extension  (RFC  6962).   This  feature    requires
              OpenSSL   >=   1.0.2.    See   also --tls-sct-dir option.

       --dh-param-file=<PATH>
              Path  to  file  that contains  DH parameters in PEM format.  Without  this   option,  DHE   cipher
              suites   are  not available.

       --npn-list=<LIST>
              Comma delimited list of  ALPN protocol identifier sorted in the  order of preference.  That  means
              most  desirable  protocol comes  first.  This  is used  in both  ALPN and NPN.  The parameter must
              be  delimited by a single comma only  and any  white spaces  are  treated as  a part  of  protocol
              string.

              Default: h2,h2-16,h2-14,http/1.1

       --verify-client
              Require and verify client certificate.

       --verify-client-cacert=<PATH>
              Path   to file  that contains  CA certificates  to verify client certificate.  The file must be in
              PEM format.  It can contain multiple certificates.

       --verify-client-tolerate-expired
              Accept  expired  client  certificate.   Operator  should handle  the expired  client   certificate
              by some  means (e.g.,  mruby  script).   Otherwise, this  option  might cause a security risk.

       --client-private-key-file=<PATH>
              Path to  file that contains  client private key  used in backend client authentication.

       --client-cert-file=<PATH>
              Path to  file that  contains client certificate  used in backend client authentication.

       --tls-min-proto-version=<VER>
              Specify  minimum  SSL/TLS  protocol.   The name matching is done in  case-insensitive manner.  The
              versions  between  --tls-min-proto-version  and   --tls-max-proto-version  are  enabled.   If  the
              protocol  list  advertised by client does not  overlap  this range,  you  will  receive the  error
              message "unknown protocol".  If a protocol version lower than TLSv1.2 is specified, make sure that
              the  compatible  ciphers  are   included  in  --ciphers  option.    The default cipher  list  only
              includes  ciphers  compatible  with TLSv1.2  or  above.   The  available  versions  are:  TLSv1.3,
              TLSv1.2, TLSv1.1, and TLSv1.0

              Default: TLSv1.2

       --tls-max-proto-version=<VER>
              Specify  maximum  SSL/TLS  protocol.   The name matching is done in  case-insensitive manner.  The
              versions  between  --tls-min-proto-version  and   --tls-max-proto-version  are  enabled.   If  the
              protocol  list  advertised by client does not  overlap  this range,  you  will  receive the  error
              message "unknown protocol".  The available versions are: TLSv1.3, TLSv1.2, TLSv1.1, and TLSv1.0

              Default: TLSv1.3

       --tls-ticket-key-file=<PATH>
              Path to file that  contains   random  data  to  construct  TLS  session  ticket   parameters.   If
              aes-128-cbc  is   given  in  --tls-ticket-key-cipher, the  file must  contain exactly 48    bytes.
              If     aes-256-cbc    is    given    in --tls-ticket-key-cipher, the  file must   contain  exactly
              80  bytes.   This  options  can be  used  repeatedly  to specify  multiple ticket  parameters.  If
              several files are given,  only the  first key is  used to  encrypt TLS  session   tickets.   Other
              keys  are   accepted  but   server will  issue new  session  ticket with  first key.   This allows
              session  key  rotation.  Please  note  that  key rotation  does  not  occur automatically.    User
              should  rearrange   files or  change options  values and  restart nghttpx gracefully.   If opening
              or reading  given file fails, all loaded  keys are discarded and  it is treated  as  if  none   of
              this option is given.  If  this option is not given or an error  occurred while opening or reading
              a file,  key is  generated every  1 hour  internally and they are  valid for  12 hours.   This  is
              recommended if ticket  key sharing  between  nghttpx  instances is  not required.

       --tls-ticket-key-memcached=<HOST>,<PORT>[;tls]
              Specify  address   of  memcached   server  to get  TLS ticket keys for  session resumption.   This
              enables  shared TLS ticket key between  multiple nghttpx instances.   nghttpx  does  not  set  TLS
              ticket   key  to memcached.  The external ticket key generator is required.  nghttpx just gets TLS
              ticket  keys  from  memcached, and  use  them,  possibly replacing current set  of keys.  It is up
              to  extern  TLS  ticket   key  generator   to  rotate  keys frequently.   See "TLS SESSION  TICKET
              RESUMPTION" section in  manual page to know the  data  format  in  memcached  entry.   Optionally,
              memcached  connection  can  be  encrypted  with  TLS  by specifying "tls" parameter.

       --tls-ticket-key-memcached-address-family=(auto|IPv4|IPv6)
              Specify  address   family  of  memcached connections  to get TLS ticket keys.  If "auto" is given,
              both IPv4 and IPv6 are considered.   If "IPv4" is given,  only IPv4  address  is  considered.   If
              "IPv6" is given, only IPv6 address is considered.

              Default: auto

       --tls-ticket-key-memcached-interval=<DURATION>
              Set interval to get TLS ticket keys from memcached.

              Default: 10m

       --tls-ticket-key-memcached-max-retry=<N>
              Set  maximum   number  of  consecutive   retries  before abandoning TLS ticket key  retrieval.  If
              this number is reached,  the  attempt  is  considered   as   failure,   and  "failure"  count   is
              incremented  by  1,   which  contributed  to            the            value            controlled
              --tls-ticket-key-memcached-max-fail option.

              Default: 3

       --tls-ticket-key-memcached-max-fail=<N>
              Set  maximum   number  of  consecutive   failure  before disabling TLS ticket until next scheduled
              key retrieval.

              Default: 2

       --tls-ticket-key-cipher=<CIPHER>
              Specify  cipher   to encrypt TLS session  ticket.  Specify either   aes-128-cbc   or  aes-256-cbc.
              By   default, aes-128-cbc is used.

       --tls-ticket-key-memcached-cert-file=<PATH>
              Path to client certificate  for memcached connections to get TLS ticket keys.

       --tls-ticket-key-memcached-private-key-file=<PATH>
              Path to client private  key for memcached connections to get TLS ticket keys.

       --fetch-ocsp-response-file=<PATH>
              Path to  fetch-ocsp-response script file.  It  should be absolute path.

              Default: /usr/local/share/nghttp2/fetch-ocsp-response

       --ocsp-update-interval=<DURATION>
              Set interval to update OCSP response cache.

              Default: 4h

       --ocsp-startup
              Start  accepting connections  after initial  attempts to get OCSP responses  finish.  It does  not
              matter  some  of  the   attempts  fail.  This  feature  is  useful if  OCSP responses   must    be
              available    before   accepting connections.

       --no-verify-ocsp
              nghttpx does not verify OCSP response.

       --no-ocsp
              Disable OCSP stapling.

       --tls-session-cache-memcached=<HOST>,<PORT>[;tls]
              Specify  address of  memcached server  to store  session cache.   This  enables   shared   session
              cache   between  multiple    nghttpx   instances.     Optionally,   memcached  connection  can  be
              encrypted with TLS by specifying "tls" parameter.

       --tls-session-cache-memcached-address-family=(auto|IPv4|IPv6)
              Specify address family of memcached connections to store session cache.  If  "auto" is given, both
              IPv4  and  IPv6 are considered.   If "IPv4" is given,  only IPv4 address is considered.  If "IPv6"
              is given, only IPv6 address is considered.

              Default: auto

       --tls-session-cache-memcached-cert-file=<PATH>
              Path to client certificate  for memcached connections to store session cache.

       --tls-session-cache-memcached-private-key-file=<PATH>
              Path to client private  key for memcached connections to store session cache.

       --tls-dyn-rec-warmup-threshold=<SIZE>
              Specify the  threshold size for TLS  dynamic record size behaviour.  During  a TLS  session, after
              the  threshold  number  of bytes  have been written, the  TLS record size will be increased to the
              maximum allowed (16K).  The max record size will  continue to be used on  the active TLS  session.
              After  --tls-dyn-rec-idle-timeout has elapsed, the record size is reduced  to 1300 bytes.  Specify
              0 to always use  the maximum record size,  regardless of idle period.   This   behaviour   applies
              to  all  TLS  based frontends, and TLS HTTP/2 backends.

              Default: 1M

       --tls-dyn-rec-idle-timeout=<DURATION>
              Specify  TLS  dynamic  record   size  behaviour  timeout.  See --tls-dyn-rec-warmup-threshold  for
              more  information.  This behaviour  applies to all TLS  based frontends, and TLS HTTP/2 backends.

              Default: 1s

       --no-http2-cipher-black-list
              Allow     black     listed      cipher     suite      on      frontend      HTTP/2     connection.
              See  https://tools.ietf.org/html/rfc7540#appendix-A   for  the complete HTTP/2 cipher suites black
              list.

       --client-no-http2-cipher-black-list
              Allow     black     listed      cipher      suite      on      backend      HTTP/2     connection.
              See  https://tools.ietf.org/html/rfc7540#appendix-A   for  the complete HTTP/2 cipher suites black
              list.

       --tls-sct-dir=<DIR>
              Specifies the  directory where  *.sct files  exist.  All *.sct   files   in  <DIR>    are    read,
              and  sent   as extension_data of  TLS signed_certificate_timestamp (RFC 6962)  to  client.   These
              *.sct  files  are  for  the certificate    specified    in    positional    command-line  argument
              <CERT>,  or   certificate  option  in  configuration file.   For   additional  certificates,   use
              --subcert option.  This option requires OpenSSL >= 1.0.2.

       --psk-secrets=<PATH>
              Read list of PSK identity and secrets from <PATH>.  This is used  for  frontend  connection.   The
              each  line  of  input  file  is  formatted  as  <identity>:<hex-secret>,  where <identity> is  PSK
              identity, and <hex-secret>  is secret in hex.  An  empty line, and line which  starts with '#' are
              skipped.   The default  enabled cipher list might not contain any PSK cipher suite.  In that case,
              desired PSK cipher suites  must be  enabled using  --ciphers option.   The   desired  PSK   cipher
              suite   may be  black listed  by HTTP/2.   To  use  those   cipher  suites  with  HTTP/2, consider
              to  use  --no-http2-cipher-black-list  option.  But be aware its implications.

       --client-psk-secrets=<PATH>
              Read PSK identity and secrets from <PATH>.  This is used for backend connection.  The  each   line
              of  input  file  is  formatted  as <identity>:<hex-secret>,  where <identity> is PSK identity, and
              <hex-secret>  is secret in hex.  An empty line, and line which  starts with '#' are skipped.   The
              first  identity and  secret pair encountered is used.  The default  enabled cipher  list might not
              contain any PSK  cipher suite.   In  that case,  desired PSK   cipher  suites   must  be   enabled
              using   --client-ciphers option.  The  desired PSK  cipher suite  may be  black listed  by HTTP/2.
              To     use     those      cipher      suites      with      HTTP/2,     consider       to      use
              --client-no-http2-cipher-black-list option.  But be aware its implications.

       --tls-no-postpone-early-data
              By  default,  nghttpx postpones forwarding  HTTP requests sent in early data, including those sent
              in partially in it, until TLS handshake finishes.  If all backend server  recognizes  "Early-Data"
              header   field,  using  this  option makes nghttpx  not postpone  forwarding request  and get full
              potential of 0-RTT data.

       --tls-max-early-data=<SIZE>
              Sets  the  maximum  amount  of 0-RTT  data  that  server accepts.

              Default: 16K

   HTTP/2
       -c, --frontend-http2-max-concurrent-streams=<N>
              Set the maximum number of  the concurrent streams in one frontend HTTP/2 session.

              Default: 100

       --backend-http2-max-concurrent-streams=<N>
              Set the maximum number of  the concurrent streams in one  backend   HTTP/2  session.    This  sets
              maximum  number   of  concurrent opened pushed streams.  The maximum number of concurrent requests
              are set by a remote server.

              Default: 100

       --frontend-http2-window-size=<SIZE>
              Sets  the  per-stream  initial  window  size  of  HTTP/2 frontend connection.

              Default: 65535

       --frontend-http2-connection-window-size=<SIZE>
              Sets the  per-connection window size of  HTTP/2 frontend connection.

              Default: 65535

       --backend-http2-window-size=<SIZE>
              Sets  the   initial  window   size  of   HTTP/2  backend connection.

              Default: 65535

       --backend-http2-connection-window-size=<SIZE>
              Sets the  per-connection window  size of  HTTP/2 backend connection.

              Default: 2147483647

       --http2-no-cookie-crumbling
              Don't crumble cookie header field.

       --padding=<N>
              Add  at most  <N> bytes  to  a HTTP/2  frame payload  as padding.  Specify 0 to  disable  padding.
              This option is meant for debugging purpose  and not intended to enhance protocol security.

       --no-server-push
              Disable  HTTP/2  server  push.   Server push is supported by default mode and HTTP/2  frontend via
              Link header field.  It is  also supported if  both frontend and  backend  are  HTTP/2  in  default
              mode.   In   this  case, server push from backend session is relayed  to frontend, and server push
              via Link header field is also supported.

       --frontend-http2-optimize-write-buffer-size
              (Experimental) Enable write  buffer size optimization in frontend HTTP/2  TLS   connection.   This
              optimization  aims to reduce  write buffer  size so  that it  only contains bytes  which can  send
              immediately.   This makes  server  more  responsive  to  prioritized  HTTP/2  stream  because  the
              buffering   of lower  priority stream  is reduced.   This option is only effective on recent Linux
              platform.

       --frontend-http2-optimize-window-size
              (Experimental)   Automatically  tune   connection  level  window  size  of  frontend   HTTP/2  TLS
              connection.   If  this  feature  is   enabled,  connection  window size  starts with the   default
              window   size,   65535  bytes.    nghttpx automatically  adjusts connection  window size  based on
              TCP  receiving   window  size.   The  maximum   window  size  is capped      by      the     value
              specified      by --frontend-http2-connection-window-size.     Since   the stream  is  subject  to
              stream level window size, it should be adjusted using --frontend-http2-window-size option as well.
              This option  is only  effective on  recent Linux platform.

       --frontend-http2-encoder-dynamic-table-size=<SIZE>
              Specify the maximum dynamic  table size of HPACK encoder in the frontend HTTP/2  connection.   The
              decoder  (client)  specifies   the  maximum  dynamic table  size it  accepts.  Then the negotiated
              dynamic table size is the minimum of this option value and the value which client specified.

              Default: 4K

       --frontend-http2-decoder-dynamic-table-size=<SIZE>
              Specify the maximum dynamic  table size of HPACK decoder in the frontend HTTP/2 connection.

              Default: 4K

       --backend-http2-encoder-dynamic-table-size=<SIZE>
              Specify the maximum dynamic  table size of HPACK encoder in the backend  HTTP/2  connection.   The
              decoder  (backend)  specifies   the maximum  dynamic table  size it  accepts.  Then the negotiated
              dynamic table size is the minimum of this option value and the value which backend specified.

              Default: 4K

       --backend-http2-decoder-dynamic-table-size=<SIZE>
              Specify the maximum dynamic  table size of HPACK decoder in the backend HTTP/2 connection.

              Default: 4K

   Mode
       (default mode)
              Accept  HTTP/2,  and  HTTP/1.1 over  SSL/TLS.   "no-tls" parameter is  used in  --frontend option,
              accept  HTTP/2  and  HTTP/1.1  over  cleartext   TCP.   The  incoming HTTP/1.1 connection  can  be
              upgraded  to  HTTP/2  through  HTTP Upgrade.

       -s, --http2-proxy
              Like default mode, but enable forward proxy.  This is so called HTTP/2 proxy mode.

   Logging
       -L, --log-level=<LEVEL>
              Set the severity  level of log output.   <LEVEL> must be one of  INFO,  NOTICE,  WARN,  ERROR  and
              FATAL.

              Default: NOTICE

       --accesslog-file=<PATH>
              Set path to write access log.  To reopen file, send USR1 signal to nghttpx.

       --accesslog-syslog
              Send  access log  to syslog.   If this  option is  used, --accesslog-file option is ignored.

       --accesslog-format=<FORMAT>
              Specify   format   string   for  access   log.    The   default  format  is combined format.   The
              following variables are available:

              • $remote_addr: client IP address.

              • $time_local: local time in Common Log format.

              • $time_iso8601: local time in ISO 8601 format.

              • $request: HTTP request line.

              • $status: HTTP response status code.

              • $body_bytes_sent: the  number of bytes sent  to client as response body.

              • $http_<VAR>: value of HTTP  request header <VAR> where '_' in <VAR> is replaced with '-'.

              • $remote_port: client  port.

              • $server_port: server port.

              • $request_time: request processing time in seconds with milliseconds resolution.

              • $pid: PID of the running process.

              • $alpn: ALPN identifier of the protocol which generates the  response.    For  HTTP/1,   ALPN  is
                always http/1.1, regardless of minor version.

              • $tls_cipher: cipher used for SSL/TLS connection.

              • $tls_client_fingerprint_sha256: SHA-256 fingerprint of client certificate.

              • $tls_client_fingerprint_sha1:  SHA-1   fingerprint  of client certificate.

              • $tls_client_subject_name:   subject  name   in  client certificate.

              • $tls_client_issuer_name:   issuer   name   in   client certificate.

              • $tls_client_serial:    serial    number   in    client certificate.

              • $tls_protocol: protocol for SSL/TLS connection.

              • $tls_session_id: session ID for SSL/TLS connection.

              • $tls_session_reused:  "r"   if  SSL/TLS   session  was reused.  Otherwise, "."

              • $tls_sni: SNI server name for SSL/TLS connection.

              • $backend_host:   backend   host    used   to   fulfill  the request.  "-" if backend host is not
                available.

              • $backend_port:  backend  port   used  to  fulfill  the request.  "-"  if  backend  host  is  not
                available.

              The  variable  can  be  enclosed  by  "{"  and  "}"  for disambiguation (e.g., ${remote_addr}).

              Default:  $remote_addr  -  -  [$time_local]  "$request"  $status  $body_bytes_sent "$http_referer"
              "$http_user_agent"

       --accesslog-write-early
              Write  access  log  when   response  header  fields  are received   from  backend   rather    than
              when   request transaction finishes.

       --errorlog-file=<PATH>
              Set  path  to  write  error  log.  To reopen file, send USR1 signal  to nghttpx.   stderr will  be
              redirected  to the error log file unless --errorlog-syslog is used.

              Default: /dev/stderr

       --errorlog-syslog
              Send  error log  to  syslog.  If  this  option is  used, --errorlog-file option is ignored.

       --syslog-facility=<FACILITY>
              Set syslog facility to <FACILITY>.

              Default: daemon

   HTTP
       --add-x-forwarded-for
              Append  X-Forwarded-For header  field to  the downstream request.

       --strip-incoming-x-forwarded-for
              Strip X-Forwarded-For  header field from  inbound client requests.

       --no-add-x-forwarded-proto
              Don't append  additional X-Forwarded-Proto  header field to  the   backend  request.   If  inbound
              client            sets           X-Forwarded-Proto,                                            and
              --no-strip-incoming-x-forwarded-proto  option  is  used, they are passed to the backend.

       --no-strip-incoming-x-forwarded-proto
              Don't strip X-Forwarded-Proto  header field from inbound client requests.

       --add-forwarded=<LIST>
              Append RFC  7239 Forwarded header field  with parameters specified in comma delimited list <LIST>.
              The  supported  parameters   are  "by",  "for", "host",  and "proto".   By default,  the value  of
              "by"  and   "for"  parameters   are  obfuscated      string.      See      --forwarded-by      and
              --forwarded-for  options  respectively.   Note  that  nghttpx  does   not   translate non-standard
              X-Forwarded-*  header fields into Forwarded header field, and vice versa.

       --strip-incoming-forwarded
              Strip  Forwarded   header  field  from   inbound  client requests.

       --forwarded-by=(obfuscated|ip|<VALUE>)
              Specify the parameter value sent  out  with  "by"  parameter  of  Forwarded   header  field.    If
              "obfuscated"   is  given,  the  string  is randomly generated at startup.  If "ip" is given,   the
              interface   address  of   the  connection, including port number, is  sent  with  "by"  parameter.
              In  case  of UNIX domain  socket, "localhost" is used instead of address and  port.  User can also
              specify the static obfuscated string.  The limitation is that  it  must  start  with    "_",   and
              only   consists   of  character   set [A-Za-z0-9._-], as described in RFC 7239.

              Default: obfuscated

       --forwarded-for=(obfuscated|ip)
              Specify   the   parameter  value  sent  out   with  "for" parameter of Forwarded header field.  If
              "obfuscated" is given, the string is  randomly generated for each client connection.  If  "ip"  is
              given,  the  remote  client address of  the connection,  without port  number, is  sent with "for"
              parameter.   In  case   of  UNIX  domain  socket, "localhost" is used instead of address.

              Default: obfuscated

       --no-via
              Don't append to  Via header field.  If  Via header field is received, it is left unaltered.

       --no-strip-incoming-early-data
              Don't strip Early-Data header  field from inbound client requests.

       --no-location-rewrite
              Don't  rewrite location  header field  in default  mode.  When --http2-proxy   is  used,  location
              header  field will not be altered regardless of this option.

       --host-rewrite
              Rewrite   host  and   :authority  header   fields in  default mode.  When  --http2-proxy is  used,
              these  headers will not be altered regardless of this option.

       --altsvc=<PROTOID,PORT[,HOST,[ORIGIN]]>
              Specify   protocol  ID,   port,   host    and   origin    of  alternative  service.   <HOST>   and
              <ORIGIN>  are  optional.   They   are  advertised   in   alt-svc  header   field only  in HTTP/1.1
              frontend.  This  option can  be  used   multiple  times    to    specify   multiple    alternative
              services.  Example: --altsvc=h2,443

       --add-request-header=<HEADER>
              Specify  additional  header field to add to request header set.  This  option just  appends header
              field  and won't replace anything  already set.  This option  can  be  used  several   times    to
              specify  multiple   header  fields.  Example: --add-request-header="foo: bar"

       --add-response-header=<HEADER>
              Specify   additional   header   field to  add  to  response header set.   This option just appends
              header field and won't replace anything already  set.  This option can be used several   times  to
              specify multiple  header fields.  Example: --add-response-header="foo: bar"

       --request-header-field-buffer=<SIZE>
              Set  maximum  buffer  size for incoming HTTP request header field list.  This is the sum of header
              name and value in bytes.   If  trailer  fields  exist,  they  are  counted towards this number.

              Default: 64K

       --max-request-header-fields=<N>
              Set  maximum  number  of incoming  HTTP  request  header  fields.    If   trailer   fields  exist,
              they  are  counted towards this number.

              Default: 100

       --response-header-field-buffer=<SIZE>
              Set   maximum   buffer  size for  incoming  HTTP  response header field list.   This is the sum of
              header name and value  in  bytes.  If  trailer  fields  exist,  they   are  counted  towards  this
              number.

              Default: 64K

       --max-response-header-fields=<N>
              Set   maximum  number   of   incoming   HTTP response  header fields.   If  trailer  fields exist,
              they  are  counted towards this number.

              Default: 500

       --error-page=(<CODE>|*)=<PATH>
              Set file path  to custom error page  served when nghttpx originally  generates  HTTP  error status
              code   <CODE>.   <CODE>  must  be  greater than or equal to 400, and at most 599.  If "*"  is used
              instead of <CODE>,  it matches all HTTP  status   code.   If   error   status   code  comes   from
              backend server, the custom error pages are not used.

       --server-name=<NAME>
              Change server response header field value to <NAME>.

              Default: nghttpx

       --no-server-rewrite
              Don't rewrite server header field in default mode.  When --http2-proxy is used, these headers will
              not be altered regardless of this option.

       --redirect-https-port=<PORT>
              Specify the port number which appears in Location header field  when  redirect  to  HTTPS  URI  is
              made  due  to "redirect-if-not-tls" parameter in --backend option.

              Default: 443

   API
       --api-max-request-body=<SIZE>
              Set the maximum size of request body for API request.

              Default: 32M

   DNS
       --dns-cache-timeout=<DURATION>
              Set  duration  that  cached  DNS  results remain valid.  Note that nghttpx caches the unsuccessful
              results as well.

              Default: 10s

       --dns-lookup-timeout=<DURATION>
              Set timeout that  DNS server is given to  respond to the initial  DNS  query.  For  the  2nd   and
              later  queries, server is  given time based  on this timeout, and  it is scaled linearly.

              Default: 5s

       --dns-max-try=<N>
              Set the number of DNS query before nghttpx gives up name lookup.

              Default: 2

       --frontend-max-requests=<N>
              The  number   of  requests that single  frontend connection can process.  For HTTP/2, this  is the
              number of streams in  one  HTTP/2 connection.   For  HTTP/1,  this is  the number  of  keep  alive
              requests.  This is hint to nghttpx, and it  may allow additional few  requests.  The default value
              is unlimited.

   Debug
       --frontend-http2-dump-request-header=<PATH>
              Dumps request headers received by HTTP/2 frontend to the file denoted  in <PATH>.  The  output  is
              done   in  HTTP/1  header  field  format and each header block is followed by an empty line.  This
              option  is not thread safe and MUST NOT be used with option -n<N>, where <N> >= 2.

       --frontend-http2-dump-response-header=<PATH>
              Dumps response headers sent  from HTTP/2 frontend to the file denoted  in <PATH>.  The  output  is
              done   in  HTTP/1  header  field  format and each header block is followed by an empty line.  This
              option  is not thread safe and MUST NOT be used with option -n<N>, where <N> >= 2.

       -o, --frontend-frame-debug
              Print HTTP/2 frames in  frontend to stderr.  This option is  not thread  safe and   MUST  NOT   be
              used  with option -n=N, where N >= 2.

   Process
       -D, --daemon
              Run in a background.  If -D is used, the current working directory is changed to '/'.

       --pid-file=<PATH>
              Set path to save PID of this program.

       --user=<USER>
              Run this program as <USER>.   This option is intended to be used to drop root privileges.

       --single-process
              Run  this  program in a  single process mode for debugging purpose.  Without this option,  nghttpx
              creates at least 2  processes:  master  and worker  processes.   If  this option is  used,  master
              and  worker   are  unified   into  a  single  process.  nghttpx still spawns additional process if
              neverbleed is used.  In  the single process mode, the signal handling feature is disabled.

   Scripting
       --mruby-file=<PATH>
              Set mruby script file

       --ignore-per-pattern-mruby-error
              Ignore mruby compile error  for per-pattern mruby script file.  If error  occurred, it is  treated
              as  if no mruby file were specified for the pattern.

   Misc
       --conf=<PATH>
              Load   configuration   from    <PATH>.    Please   note   that  nghttpx  always  tries to read the
              default configuration file if --conf is not given.

              Default: /etc/nghttpx/nghttpx.conf

       --include=<PATH>
              Load additional configurations from <PATH>.  File <PATH> is   read   when   configuration   parser
              encountered  this option.  This option can be used multiple times, or even recursively.

       -v, --version
              Print version and exit.

       -h, --help
              Print this help and exit.

       The  <SIZE>  argument  is an integer and an optional unit (e.g., 10K is 10 * 1024).  Units are K, M and G
       (powers of 1024).

       The <DURATION> argument is an integer and an optional unit (e.g.,  1s  is  1  second  and  500ms  is  500
       milliseconds).   Units  are h, m, s or ms (hours, minutes, seconds and milliseconds, respectively).  If a
       unit is omitted, a second is used as unit.

FILES

       /etc/nghttpx/nghttpx.conf
              The default configuration file path nghttpx searches at startup.  The configuration file path  can
              be changed using --conf option.

              Those lines which are staring # are treated as comment.

              The  option  name  in  the configuration file is the long command-line option name with leading --
              stripped (e.g., frontend).  Put = between option name and  value.   Don't  put  extra  leading  or
              trailing spaces.

              When  specifying  arguments including characters which have special meaning to a shell, we usually
              use quotes so that shell does not interpret them.  When writing this  configuration  file,  quotes
              for this purpose must not be used.  For example, specify additional request header field, do this:

                 add-request-header=foo: bar

              instead of:

                 add-request-header="foo: bar"

              The  options  which  do  not  take argument in the command-line take argument in the configuration
              file.  Specify yes as an argument (e.g., http2-proxy=yes).   If  other  string  is  given,  it  is
              ignored.

              To  specify  private  key  and  certificate  file  which  are  given  as  positional  arguments in
              command-line, use private-key-file and certificate-file.

              --conf option cannot be used in the configuration file and will be ignored if specified.

       Error log
              Error log is written to stderr by default.  It  can  be  configured  using  --errorlog-file.   The
              format of log message is as follows:

              <datetime> <master-pid> <current-pid> <thread-id> <level> (<filename>:<line>) <msg>

              <datetime>
                     It is a combination of date and time when the log is written.  It is in ISO 8601 format.

              <master-pid>
                     It is a master process ID.

              <current-pid>
                     It is a process ID which writes this log.

              <thread-id>
                     It is a thread ID which writes this log.  It would be unique within <current-pid>.

              <filename> and <line>
                     They are source file name, and line number which produce this log.

              <msg>  It is a log message body.

SIGNALS

       SIGQUIT
              Shutdown  gracefully.   First accept pending connections and stop accepting connection.  After all
              connections are handled, nghttpx exits.

       SIGHUP Reload configuration file given in --conf.

       SIGUSR1
              Reopen log files.

       SIGUSR2
          Fork and execute nghttpx.  It will execute  the  binary  in  the  same  path  with  same  command-line
          arguments  and  environment  variables.   As  of  nghttpx version 1.20.0, the new master process sends
          SIGQUIT to the original master process when it is ready to serve requests.  For the  earlier  versions
          of nghttpx, user has to send SIGQUIT to the original master process.

          The  difference  between  SIGUSR2 (+ SIGQUIT) and SIGHUP is that former is usually used to execute new
          binary, and the master process is  newly  spawned.   On  the  other  hand,  the  latter  just  reloads
          configuration file, and the same master process continues to exist.

       NOTE:
          nghttpx  consists of multiple processes: one process for processing these signals, and another one for
          processing requests.  The former spawns the latter.  The former is  called  master  process,  and  the
          latter  is  called  worker  process.   If  neverbleed is enabled, the worker process spawns neverbleed
          daemon process which does RSA key processing.  The above signal must be sent to  the  master  process.
          If  the  other  processes  received one of them, it is ignored.  This behaviour of these processes may
          change in the future release.  In other words, in the future release, the processes other than  master
          process may terminate upon the reception of these signals.  Therefore these signals should not be sent
          to the processes other than master process.

SERVER PUSH

       nghttpx supports HTTP/2 server push in default mode with Link  header  field.   nghttpx  looks  for  Link
       header field (RFC 5988) in response headers from backend server and extracts URI-reference with parameter
       rel=preload (see preload) and pushes those URIs to the frontend client. Here  is  a  sample  Link  header
       field to initiate server push:

          Link: </fonts/font.woff>; rel=preload
          Link: </css/theme.css>; rel=preload

       Currently, the following restriction is applied for server push:

       1. The  associated  stream must have method "GET" or "POST".  The associated stream's status code must be
          200.

       This limitation may be loosened in the future release.

       nghttpx also supports server push if both frontend and backend are HTTP/2 in default mode.  In this case,
       in  addition  to  server  push  via  Link header field, server push from backend is forwarded to frontend
       HTTP/2 session.

       HTTP/2 server push will be disabled if --http2-proxy is used.

UNIX DOMAIN SOCKET

       nghttpx supports UNIX domain socket with a filename for both frontend and backend connections.

       Please note that current nghttpx implementation does not delete a socket with a filename.  And  on  start
       up, if nghttpx detects that the specified socket already exists in the file system, nghttpx first deletes
       it.  However, if SIGUSR2 is used to execute new binary and both  old  and  new  configurations  use  same
       filename, new binary does not delete the socket and continues to use it.

OCSP STAPLING

       OCSP  query is done using external Python script fetch-ocsp-response, which has been originally developed
       in Perl as part of h2o project (https://github.com/h2o/h2o), and was translated into Python.

       The script file is usually installed under $(prefix)/share/nghttp2/ directory.  The actual path to script
       can be customized using --fetch-ocsp-response-file option.

       If OCSP query is failed, previous OCSP response, if any, is continued to be used.

       --fetch-ocsp-response-file  option  provides  wide  range of possibility to manage OCSP response.  It can
       take an arbitrary script or executable.  The requirement is that it supports the  command-line  interface
       of  fetch-ocsp-response script, and it must return a valid DER encoded OCSP response on success.  It must
       return exit code 0 on success, and 75 for temporary error, and the other error code for generic  failure.
       For  large  cluster  of  servers,  it  is  not  efficient  for  each  server  to perform OCSP query using
       fetch-ocsp-response.  Instead, you can retrieve OCSP response in some way, and store it in a  disk  or  a
       shared  database.   Then  specify  a program in --fetch-ocsp-response-file to fetch it from those stores.
       This could provide a way to share the OCSP response between fleet of servers, and  also  any  OCSP  query
       strategy can be applied which may be beyond the ability of nghttpx itself or fetch-ocsp-response script.

TLS SESSION RESUMPTION

       nghttpx supports TLS session resumption through both session ID and session ticket.

   SESSION ID RESUMPTION
       By default, session ID is shared by all worker threads.

       If  --tls-session-cache-memcached is given, nghttpx will insert serialized session data to memcached with
       nghttpx:tls-session-cache: + lowercase hex string of session ID as a memcached  entry  key,  with  expiry
       time 12 hours.  Session timeout is set to 12 hours.

       By  default, connections to memcached server are not encrypted.  To enable encryption, use tls keyword in
       --tls-session-cache-memcached option.

   TLS SESSION TICKET RESUMPTION
       By default, session ticket is shared by all worker threads.  The automatic key rotation is  also  enabled
       by  default.   Every  an  hour,  new  encryption  key  is  generated, and previous encryption key becomes
       decryption only key.  We set session timeout to 12 hours, and thus we keep at most 12 keys.

       If --tls-ticket-key-memcached is given, encryption keys are retrieved from memcached.  nghttpx just reads
       keys  from  memcached;  one  has to deploy key generator program to update keys frequently (e.g., every 1
       hour).  The example key generator tlsticketupdate.go is available  under  contrib  directory  in  nghttp2
       archive.   The memcached entry key is nghttpx:tls-ticket-key.  The data format stored in memcached is the
       binary format described below:

          +--------------+-------+----------------+
          | VERSION (4)  |LEN (2)|KEY(48 or 80) ...
          +--------------+-------+----------------+
                         ^                        |
                         |                        |
                         +------------------------+
                         (LEN, KEY) pair can be repeated

       All numbers in the above figure is bytes.  All integer fields are network byte order.

       First 4 bytes integer VERSION field, which must be 1.  The 2 bytes integer LEN field gives the length  of
       following KEY field, which contains key.  If --tls-ticket-key-cipher=aes-128-cbc is used, LEN must be 48.
       If --tls-ticket-key-cipher=aes-256-cbc is used, LEN must be  80.   LEN  and  KEY  pair  can  be  repeated
       multiple  times  to  store  multiple  keys.   The  key appeared first is used as encryption key.  All the
       remaining keys are used as decryption only.

       By default, connections to memcached server are not encrypted.  To enable encryption, use tls keyword  in
       --tls-ticket-key-memcached option.

       If  --tls-ticket-key-file  is  given,  encryption key is read from the given file.  In this case, nghttpx
       does not rotate key automatically.  To rotate key, one has to restart nghttpx (see SIGNALS).

CERTIFICATE TRANSPARENCY

       nghttpx supports TLS  signed_certificate_timestamp  extension  (RFC  6962).   The  relevant  options  are
       --tls-sct-dir  and  sct-dir  parameter in --subcert.  They takes a directory, and nghttpx reads all files
       whose extension is .sct under the directory.  The *.sct files are encoded  as  SignedCertificateTimestamp
       struct  described  in  section  3.2  of  RFC  69662.   This  format  is the same one used by nginx-ct and
       mod_ssl_ct.   ct-submit  can  be  used  to  submit  certificates  to  log   servers,   and   obtain   the
       SignedCertificateTimestamp struct which can be used with nghttpx.

MRUBY SCRIPTING

       WARNING:
          The  current  mruby extension API is experimental and not frozen.  The API is subject to change in the
          future release.

       WARNING:
          Almost all string value returned from method, or attribute is a fresh new mruby string, which involves
          memory  allocation,  and  copies.   Therefore, it is strongly recommended to store a return value in a
          local variable, and use it, instead of calling method or accessing attribute repeatedly.

       nghttpx allows users to extend its capability using mruby scripts.  nghttpx has 2 hook points to  execute
       mruby  script:  request  phase  and  response phase.  The request phase hook is invoked after all request
       header fields are received from client.  The response phase hook is invoked  after  all  response  header
       fields  are  received  from  backend server.  These hooks allows users to modify header fields, or common
       HTTP variables, like authority or request path,  and  even  return  custom  response  without  forwarding
       request to backend servers.

       There  are  2 levels of mruby script invocations: global and per-pattern.  The global mruby script is set
       by --mruby-file option and is called for all requests.  The per-pattern mruby script is  set  by  "mruby"
       parameter  in -b option.  It is invoked for a request which matches the particular pattern.  The order of
       hook invocation is: global request phase hook, per-pattern request phase hook, per-pattern response phase
       hook,  and  finally  global  response  phase hook.  If a hook returns a response, any later hooks are not
       invoked.  The global request hook is invoked before the pattern matching is  made  and  changing  request
       path may affect the pattern matching.

       Please  note  that  request and response hooks of per-pattern mruby script for a single request might not
       come from the same script.  This might happen after a request hook is executed, backend failed  for  some
       reason, and at the same time, backend configuration is replaced by API request, and then the request uses
       new configuration on retry.  The response hook from new  configuration,  if  it  is  specified,  will  be
       invoked.

       The  all  mruby  script  will be evaluated once per thread on startup, and it must instantiate object and
       evaluate it as the return value (e.g., App.new).  This object  is  called  app  object.   If  app  object
       defines  on_req  method, it is called with Nghttpx::Env object on request hook.  Similarly, if app object
       defines on_resp method, it is called  with  Nghttpx::Env  object  on  response  hook.   For  each  method
       invocation,  user  can can access Nghttpx::Request and Nghttpx::Response objects via Nghttpx::Env#req and
       Nghttpx::Env#resp respectively.

       Nghttpx::REQUEST_PHASE
              Constant to represent request phase.

       Nghttpx::RESPONSE_PHASE
              Constant to represent response phase.

       class Nghttpx::Env
              Object to represent current request specific context.

              attribute [R] req
                     Return Request object.

              attribute [R] resp
                     Return Response object.

              attribute [R] ctx
                     Return Ruby hash object.  It persists until request finishes.  So  values  set  in  request
                     phase hook can be retrieved in response phase hook.

              attribute [R] phase
                     Return the current phase.

              attribute [R] remote_addr
                     Return  IP  address of a remote client.  If connection is made via UNIX domain socket, this
                     returns the string "localhost".

              attribute [R] server_addr
                     Return address of server that accepted the connection.  This is a string which specified in
                     --frontend  option,  excluding port number, and not a resolved IP address.  For UNIX domain
                     socket, this is a path to UNIX domain socket.

              attribute [R] server_port
                     Return port number of the server frontend which accepted the connection from client.

              attribute [R] tls_used
                     Return true if TLS is used on the connection.

              attribute [R] tls_sni
                     Return the TLS SNI value which client sent in this connection.

              attribute [R] tls_client_fingerprint_sha256
                     Return the SHA-256 fingerprint of a client certificate.

              attribute [R] tls_client_fingerprint_sha1
                     Return the SHA-1 fingerprint of a client certificate.

              attribute [R] tls_client_issuer_name
                     Return the issuer name of a client certificate.

              attribute [R] tls_client_subject_name
                     Return the subject name of a client certificate.

              attribute [R] tls_client_serial
                     Return the serial number of a client certificate.

              attribute [R] tls_client_not_before
                     Return the start date of a client certificate in seconds since the epoch.

              attribute [R] tls_client_not_after
                     Return the end date of a client certificate in seconds since the epoch.

              attribute [R] tls_cipher
                     Return a TLS cipher negotiated in this connection.

              attribute [R] tls_protocol
                     Return a TLS protocol version negotiated in this connection.

              attribute [R] tls_session_id
                     Return a session ID for this connection in hex string.

              attribute [R] tls_session_reused
                     Return true if, and only if a SSL/TLS session is reused.

              attribute [R] alpn
                     Return ALPN identifier negotiated in this connection.

              attribute [R] tls_handshake_finished
                     Return true if SSL/TLS handshake has finished.  If it returns false in  the  request  phase
                     hook,  the request is received in TLSv1.3 early data (0-RTT) and might be vulnerable to the
                     replay attack.  nghttpx will send Early-Data header field to backend  servers  to  indicate
                     this.

       class Nghttpx::Request
              Object  to  represent  request from client.  The modification to Request object is allowed only in
              request phase hook.

              attribute [R] http_version_major
                     Return HTTP major version.

              attribute [R] http_version_minor
                     Return HTTP minor version.

              attribute [R/W] method
                     HTTP method.  On assignment, copy of given value is assigned.  We  don't  accept  arbitrary
                     method  name.  We will document them later, but well known methods, like GET, PUT and POST,
                     are all supported.

              attribute [R/W] authority
                     Authority (i.e., example.org), including optional port component .  On assignment, copy  of
                     given value is assigned.

              attribute [R/W] scheme
                     Scheme (i.e., http, https).  On assignment, copy of given value is assigned.

              attribute [R/W] path
                     Request  path, including query component (i.e., /index.html).  On assignment, copy of given
                     value is assigned.  The path does not include authority component of URI.  This may include
                     query   component.    nghttpx   makes   certain   normalization   for   path.   It  decodes
                     percent-encoding            for            unreserved            characters            (see
                     https://tools.ietf.org/html/rfc3986#section-2.3),  and  resolves  ".." and ".".  But it may
                     leave characters which should be percent-encoded as is. So be careful when  comparing  path
                     against desired string.

              attribute [R] headers
                     Return  Ruby  hash  containing  copy of request header fields.  Changing values in returned
                     hash does not change request header  fields  actually  used  in  request  processing.   Use
                     Nghttpx::Request#add_header or Nghttpx::Request#set_header to change request header fields.

              add_header(key, value)
                     Add  header  entry associated with key.  The value can be single string or array of string.
                     It does not replace any existing values associated with key.

              set_header(key, value)
                     Set header entry associated with key.  The value can be single string or array  of  string.
                     It replaces any existing values associated with key.

              clear_headers()
                     Clear all existing request header fields.

              push(uri)
                     Initiate  to  push resource identified by uri.  Only HTTP/2 protocol supports this feature.
                     For the other protocols, this method is noop.  uri can be absolute URI,  absolute  path  or
                     relative  path to the current request.  For absolute or relative path, scheme and authority
                     are inherited from the current request.  Currently, method is  always  GET.   nghttpx  will
                     issue  request  to backend servers to fulfill this request.  The request and response phase
                     hooks will be called for pushed resource as well.

       class Nghttpx::Response
              Object to represent response from backend server.

              attribute [R] http_version_major
                     Return HTTP major version.

              attribute [R] http_version_minor
                     Return HTTP minor version.

              attribute [R/W] status
                     HTTP status code.  It must be in the range [200, 999],  inclusive.   The  non-final  status
                     code is not supported in mruby scripting at the moment.

              attribute [R] headers
                     Return  Ruby  hash  containing copy of response header fields.  Changing values in returned
                     hash does not change response header fields actually  used  in  response  processing.   Use
                     Nghttpx::Response#add_header  or  Nghttpx::Response#set_header  to  change  response header
                     fields.

              add_header(key, value)
                     Add header entry associated with key.  The value can be single string or array  of  string.
                     It does not replace any existing values associated with key.

              set_header(key, value)
                     Set  header  entry associated with key.  The value can be single string or array of string.
                     It replaces any existing values associated with key.

              clear_headers()
                     Clear all existing response header fields.

              return(body)
                     Return custom response body to a client.  When this method is called in request phase hook,
                     the  request is not forwarded to the backend, and response phase hook for this request will
                     not be invoked.  When this method is called in response phase hook, response  from  backend
                     server is canceled and discarded.  The status code and response header fields should be set
                     before using this method.  To set status code,  use  Nghttpx::Response#status.   If  status
                     code  is not set, 200 is used.  To set response header fields, Nghttpx::Response#add_header
                     and Nghttpx::Response#set_header.  When this method is invoked in response phase hook,  the
                     response headers are filled with the ones received from backend server.  To send completely
                     custom header fields, first call  Nghttpx::Response#clear_headers  to  erase  all  existing
                     header  fields,  and  then  add required header fields.  It is an error to call this method
                     twice for a given request.

              send_info(status, headers)
                     Send non-final (informational) response to a client.  status must be  in  the  range  [100,
                     199],  inclusive.   headers is a hash containing response header fields.  Its key must be a
                     string, and the associated value must be either string or array of strings.  Since this  is
                     not  a  final  response,  even  if  this method is invoked, request is still forwarded to a
                     backend unless Nghttpx::Response#return is called.  This  method  can  be  called  multiple
                     times.  It cannot be called after Nghttpx::Response#return is called.

   MRUBY EXAMPLES
       Modify request path:

          class App
            def on_req(env)
              env.req.path = "/apps#{env.req.path}"
            end
          end

          App.new

       Don't forget to instantiate and evaluate object at the last line.

       Restrict permission of viewing a content to a specific client addresses:

          class App
            def on_req(env)
              allowed_clients = ["127.0.0.1", "::1"]

              if env.req.path.start_with?("/log/") &&
                 !allowed_clients.include?(env.remote_addr) then
                env.resp.status = 404
                env.resp.return "permission denied"
              end
            end
          end

          App.new

API ENDPOINTS

       nghttpx exposes API endpoints to manipulate it via HTTP based API.  By default, API endpoint is disabled.
       To enable it, add a dedicated frontend for  API  using  --frontend  option  with  "api"  parameter.   All
       requests which come from this frontend address, will be treated as API request.

       The response is normally JSON dictionary, and at least includes the following keys:

       status The status of the request processing.  The following values are defined:

              Success
                     The request was successful.

              Failure
                     The request was failed.  No change has been made.

       code   HTTP status code

       Additionally,  depending  on  the  API  endpoint, data key may be present, and its value contains the API
       endpoint specific data.

       We wrote "normally", since nghttpx may return ordinal HTML response in some cases  where  the  error  has
       occurred before reaching API endpoint (e.g., header field is too large).

       The following section describes available API endpoints.

   POST /api/v1beta1/backendconfig
       This API replaces the current backend server settings with the requested ones.  The request method should
       be POST, but PUT is also acceptable.  The request body must be nghttpx configuration  file  format.   For
       configuration  file format, see FILES section.  The line separator inside the request body must be single
       LF (0x0A).  Currently, only backend option is parsed, the others are simply ignored.   The  semantics  of
       this  API  is replace the current backend with the backend options in request body.  Describe the desired
       set of backend severs, and nghttpx makes it happen.  If there is no backend option is  found  in  request
       body,  the  current  set  of  backend  is  replaced  with  the  backend  option's default value, which is
       127.0.0.1,80.

       The replacement is done instantly without breaking existing connections or requests.  It also avoids  any
       process creation as is the case with hot swapping with signals.

       The  one  limitation  is  that only numeric IP address is allowed in backend in request body unless "dns"
       parameter is used while non numeric hostname is allowed in command-line or  configuration  file  is  read
       using --conf.

   GET /api/v1beta1/configrevision
       This  API  returns  configuration  revision of the current nghttpx.  The configuration revision is opaque
       string, and it changes after each reloading by SIGHUP.  With this API, an external application knows that
       whether nghttpx has finished reloading its configuration by comparing the configuration revisions between
       before and after reloading.  It is recommended to disable persistent  (keep-alive)  connection  for  this
       purpose  in  order  to  avoid  to  send  a  request using the reused connection which may bound to an old
       process.

       This API returns response including data key.  Its value is JSON object, and it  contains  at  least  the
       following key:

       configRevision
              The configuration revision of the current nghttpx

SEE ALSO

       nghttp(1), nghttpd(1), h2load(1)

AUTHOR

       Tatsuhiro Tsujikawa

COPYRIGHT

       2012, 2015, 2016, Tatsuhiro Tsujikawa