bionic (3) knet_handle_add_datafd.3.gz

Provided by: libknet-doc_1.1-1_all bug

NAME
       knet_handle_add_datafd - Install a file descriptor for communication.


SYNOPSIS
       #include <libknet.h>

       int knet_handle_add_datafd(
           knet_handle_t knet_h,
           int          *datafd,
           int8_t       *channel
       );


DESCRIPTION
       knet_handle_add_datafd

       IMPORTANT: In order to add datafd to knet, knet_handle_enable_sock_notify

       MUST  be set and be able to handle both errors (-1) and 0 bytes read / write from the provided datafd. On
       read error (< 0) from datafd, the socket is automatically removed from polling to avoid spinning on  dead
       sockets. It is safe to call knet_handle_remove_datafd even on sockets that have been removed.

       knet_h - pointer to knet_handle_t

       *datafd  - read/write file descriptor. knet will read data here to send to the other hosts and will write
       data received from the network. Each data packet can be of max  size  KNET_MAX_PACKET_SIZE!  Applications
       using  knet_send/knet_recv  will  receive  a  proper  error  if the packet size is not within boundaries.
       Applications  using  their  own  functions  to  write  to  the  datafd  should  NOT   write   more   than
       KNET_MAX_PACKET_SIZE.

       Please refer to handle.c on how to set up a socketpair.

       datafd  can be 0, and knet_handle_add_datafd will create a properly populated socket pair the same way as
       ping_test, or a value higher than 0. A negative number will return an  error.  On  exit  knet_handle_free
       will take care to cleanup the socketpair only if they have been created by knet_handle_add_datafd.

       It  is possible to pass either sockets or normal fds. User provided datafd will be marked as non-blocking
       and close-on-exit.

       *channel - This value has the same effect of VLAN tagging. A negative value will auto-allocate a channel.
       Setting a value between 0 and 31 will try to allocate that specific channel (unless already in use).

       It  is  possible  to add up to 32 datafds but be aware that each one of them must have a receiving end on
       the other host.

       Example: hostA channel 0 will be delivered to datafd on hostB channel 0 hostA channel 1 to hostB  channel
       1.

       Each channel must have a unique file descriptor.

       If  your  application could have 2 channels on one host and one channel on another host, then you can use
       dst_host_filter to manipulate channel values on TX and RX.


RETURN VALUE
       knet_handle_add_datafd returns 0          on success, *datafd will be populated  with  a  socket  if  the
       original value was 0 or if a specific fd was set, the value is untouched. *channel will be populated with
       a channel number if the original value was negative or the value is untouched if a specific  channel  was
       requested.

       -1         on error and errno is set. *datafd and *channel are untouched or empty.


SEE ALSO
       knet_handle_remove_datafd(3), knet_handle_get_stats(3), knet_host_add(3), knet_handle_pmtud_setfreq(3),
       knet_handle_pmtud_get(3), knet_host_get_id_by_host_name(3), knet_host_get_status(3),
       knet_link_get_pong_count(3), knet_link_get_priority(3), knet_handle_free(3),
       knet_handle_enable_sock_notify(3), knet_handle_get_datafd(3), knet_recv(3), knet_link_get_ping_timers(3),
       knet_log_get_subsystem_id(3), knet_host_remove(3), knet_host_enable_status_change_notify(3),
       knet_strtoaddr(3), knet_send(3), knet_handle_enable_pmtud_notify(3),
       knet_handle_get_transport_reconnect_interval(3), knet_link_get_enable(3), knet_link_set_priority(3),
       knet_log_set_loglevel(3), knet_handle_get_channel(3), knet_link_get_config(3),
       knet_link_get_link_list(3), knet_get_transport_list(3), knet_get_transport_id_by_name(3),
       knet_log_get_loglevel_id(3), knet_handle_new_ex(3), knet_host_set_name(3), knet_addrtostr(3),
       knet_handle_setfwd(3), knet_get_compress_list(3), knet_host_set_policy(3),
       knet_get_transport_name_by_id(3), knet_handle_enable_filter(3), knet_handle_compress(3),
       knet_link_get_status(3), knet_send_sync(3), knet_log_get_loglevel_name(3), knet_host_get_host_list(3),
       knet_host_get_policy(3), knet_link_set_enable(3), knet_link_set_pong_count(3),
       knet_log_get_subsystem_name(3), knet_host_get_name_by_host_id(3), knet_link_clear_config(3),
       knet_log_get_loglevel(3), knet_handle_new(3), knet_handle_pmtud_getfreq(3), knet_handle_clear_stats(3),
       knet_link_set_config(3), knet_handle_crypto(3), knet_get_crypto_list(3),
       knet_handle_set_transport_reconnect_interval(3), knet_link_set_ping_timers(3)


       Copyright (C) 2010-2018 Red Hat, Inc. All rights reserved.