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/*
mtr -- a network diagnostic tool
Copyright (C) 2016 Matt Kimball
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License version 2 as
published by the Free Software Foundation.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License along
with this program; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include "wait.h"
#include <assert.h>
#include <errno.h>
#ifdef HAVE_ERROR_H
#include <error.h>
#else
#include "portability/error.h"
#endif
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/select.h>
/*
Gather all the file descriptors which should wake our select call when
they become readable.
*/
static
int gather_read_fds(
const struct command_buffer_t *command_buffer,
const struct net_state_t *net_state,
fd_set * read_set,
fd_set * write_set)
{
int nfds;
int probe_nfds;
int ip4_socket;
int ip6_socket;
int command_stream = command_buffer->command_stream;
FD_ZERO(read_set);
FD_ZERO(write_set);
FD_SET(command_stream, read_set);
nfds = command_stream + 1;
if (net_state->platform.ip4_socket_raw) {
ip4_socket = net_state->platform.ip4_recv_socket;
FD_SET(ip4_socket, read_set);
if (ip4_socket >= nfds) {
nfds = ip4_socket + 1;
}
} else {
ip4_socket = net_state->platform.ip4_txrx_icmp_socket;
FD_SET(ip4_socket, read_set);
if (ip4_socket >= nfds) {
nfds = ip4_socket + 1;
}
ip4_socket = net_state->platform.ip4_txrx_udp_socket;
FD_SET(ip4_socket, read_set);
if (ip4_socket >= nfds) {
nfds = ip4_socket + 1;
}
}
if (net_state->platform.ip6_socket_raw) {
ip6_socket = net_state->platform.ip6_recv_socket;
FD_SET(ip6_socket, read_set);
if (ip6_socket >= nfds) {
nfds = ip6_socket + 1;
}
} else {
ip6_socket = net_state->platform.ip6_txrx_icmp_socket;
FD_SET(ip6_socket, read_set);
if (ip6_socket >= nfds) {
nfds = ip6_socket + 1;
}
ip6_socket = net_state->platform.ip6_txrx_udp_socket;
FD_SET(ip6_socket, read_set);
if (ip6_socket >= nfds) {
nfds = ip6_socket + 1;
}
}
probe_nfds = gather_probe_sockets(net_state, write_set);
if (probe_nfds > nfds) {
nfds = probe_nfds;
}
return nfds;
}
/*
Sleep until we receive a new probe response, a new command on the
command stream, or a probe timeout. On Unix systems, this means
we use select to wait on file descriptors for the command stream
and the raw receive socket.
*/
void wait_for_activity(
struct command_buffer_t *command_buffer,
struct net_state_t *net_state)
{
int nfds;
fd_set read_set;
fd_set write_set;
struct timeval probe_timeout;
struct timeval *select_timeout;
int ready_count;
nfds =
gather_read_fds(command_buffer, net_state, &read_set, &write_set);
while (true) {
select_timeout = NULL;
/* Use the soonest probe timeout time as our maximum wait time */
if (get_next_probe_timeout(net_state, &probe_timeout)) {
assert(probe_timeout.tv_sec >= 0);
select_timeout = &probe_timeout;
}
ready_count =
select(nfds, &read_set, &write_set, NULL, select_timeout);
/*
If we didn't have an error, either one of our descriptors is
readable, or we timed out. So we can now return.
*/
if (ready_count != -1) {
break;
}
/*
We will get EINTR if we received a signal during the select, so
retry in that case. We may get EAGAIN if "the kernel was
(perhaps temporarily) unable to allocate the requested number of
file descriptors." I haven't seen this in practice, but selecting
again seems like the right thing to do.
*/
if (errno != EINTR && errno != EAGAIN) {
/* We don't expect other errors, so report them */
error(EXIT_FAILURE, errno, "unexpected select error");
}
}
}
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