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knet_handle_add_datafd(3) Kronosnet Programmer's Manual knet_handle_add_datafd(3)


knet_handle_add_datafd - Install a file descriptor for communication.


#include <libknet.h>

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



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-exec.

*channel - This value is analogous to the tag in 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.


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.


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_add_acl(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_link_rm_acl(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_handle_enable_access_lists(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_pmtud_set(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_clear_acl(3), knet_link_set_ping_timers(3), knet_link_insert_acl(3)


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2020-04-23 kronosnet