Provided by: trafficserver-dev_9.1.3+ds-1_amd64 
NAME
TSClientProtocolStack - TSClientProtocolStack API function
SYNOPSIS
#include <ts/ts.h>
TSReturnCode TSHttpTxnClientProtocolStackGet(TSHttpTxn txnp, int count, char const
**result, int *actual)
TSReturnCode TSHttpTxnServerProtocolStackGet(TSHttpTxn txnp, int count, const char
**result, int *actual)
TSReturnCode TSHttpSsnClientProtocolStackGet(TSHttpSsn ssnp, int count, char const
**result, int *actual)
char const *TSHttpTxnClientProtocolStackContains(TSHttpTxn txnp)
const char *TSHttpTxnServerProtocolStackContains(TSHttpTxn txnp, char const *tag)
char const *TSHttpSsnClientProtocolStackContains(TSHttpSsn ssnp)
char const *TSNormalizedProtocolTag(char const *tag)
char const *TSRegisterProtocolTag(char const *tag)
DESCRIPTION
These functions are used to explore the protocol stack of either the client (user agent)
or origin server connection to Traffic Server. The functions
TSHttpTxnClientProtocolStackGet() and TSHttpSsnClientProtocolStackGet() can be used to
retrieve the entire protocol stack for the user agent connection. The
TSHttpTxnServerProtocolStackGet() can be used to retrieve the entire protocol stack for
the origin server connection. TSHttpTxnClientProtocolStackContains(),
TSHttpSsnClientProtocolStackContains(), and TSHttpTxnServerProtocolStackContains() will
check for a specific protocol tag being present in the stack.
Each protocol is represented by tag which is a null terminated string. A particular tag
will always be returned as the same character pointer and so protocols can be reliably
checked with pointer comparisons. TSNormalizedProtocolTag() will return this character
pointer for a specific tag. A return value of NULL indicates the provided tag is not
registered as a known protocol tag. TSRegisterProtocolTag() registers the tag and then
returns its normalized value. This is useful for plugins that provide custom protocols for
user agents.
The protocols are ordered from higher level protocols to the lower level ones on which the
higher operate. For instance a stack might look like "http/1.1,tls/1.2,tcp,ipv4". For
TSHttpTxnClientProtocolStackGet(), TSHttpSsnClientProtocolStackGet(), and
TSHttpTxnServerProtocolStackGet() these values are placed in the array result. count is
the maximum number of elements of result that may be modified by the function call. If
actual is not NULL then the actual number of elements in the protocol stack will be
returned. If this is equal or less than count then all elements were returned. If it is
larger then some layers were omitted from result. If the full stack is required actual can
be used to resize result to be sufficient to hold all of the elements and the function
called again with updated count and result. In practice the maximum number of elements is
almost certain to be less than 10 which therefore should suffice. These functions return
TS_SUCCESS on success and TS_ERROR on failure which should only occur if txnp or ssnp are
invalid.
The TSHttpTxnClientProtocolStackContains(), TSHttpSsnClientProtocolStackContains(), and
TSHttpTxnServerProtocolStackContains() functions are provided for the convenience when
only the presence of a protocol is of interest, not its location or the presence of other
protocols. These functions return NULL if the protocol tag is not present, and a pointer
to the normalized tag if it is present. The strings are matched with an anchor prefix
search, as with debug tags. For instance if tag is "tls" then it will match "tls/1.2" or
"tls/1.3". This makes checking for TLS or IP more convenient. If more precision is
required the entire protocol stack can be retrieved and processed more thoroughly.
The protocol tags defined by Traffic Server.
┌──────────┬──────────┐
│Protocol │ Tag │
├──────────┼──────────┤
│HTTP/1.1 │ http/1.1 │
├──────────┼──────────┤
│HTTP/1.0 │ http/1.0 │
├──────────┼──────────┤
│HTTP/2 │ h2 │
├──────────┼──────────┤
│WebSocket │ ws │
├──────────┼──────────┤
│TLS 1.3 │ tls/1.3 │
├──────────┼──────────┤
│TLS 1.2 │ tls/1.2 │
├──────────┼──────────┤
│TLS 1.1 │ tls/1.1 │
├──────────┼──────────┤
│TLS 1.0 │ tls/1.0 │
├──────────┼──────────┤
│TCP │ tcp │
├──────────┼──────────┤
│UDP │ udp │
├──────────┼──────────┤
│IPv4 │ ipv4 │
├──────────┼──────────┤
│IPv6 │ ipv6 │
├──────────┼──────────┤
│QUIC │ quic │
└──────────┴──────────┘
Examples
The example below is excerpted from example/plugins/c-api/protocol_stack/protocol_stack.cc
in the Traffic Server source distribution. It demonstrates how to use
TSHttpTxnClientProtocolStackGet() and TSHttpTxnClientProtocolStackContains()
static int
proto_stack_cb(TSCont contp ATS_UNUSED, TSEvent event, void *edata)
{
TSHttpTxn txnp = static_cast<TSHttpTxn>(edata);
const char *results[10];
int count = 0;
TSDebug(PLUGIN_NAME, "Protocols:");
TSHttpTxnClientProtocolStackGet(txnp, 10, results, &count);
for (int i = 0; i < count; i++) {
TSDebug(PLUGIN_NAME, "\t%d: %s", i, results[i]);
}
const char *ret_tag = TSHttpTxnClientProtocolStackContains(txnp, "h2");
TSDebug(PLUGIN_NAME, "Stack %s HTTP/2", ret_tag != nullptr ? "contains" : "does not contain");
TSHttpTxnReenable(txnp, TS_EVENT_HTTP_CONTINUE);
return 0;
}
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