Replace select(2) with poll(2)
select(2) has a number of well-known issues (e.g.: FD_SETSIZE limiting the maximum amount of file descriptors to watch) that are mostly solved by poll(2) and thus can be used as a drop-in replacement.
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@ -233,7 +233,7 @@ int handler_listen(struct handler *const h, const short port)
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for (;;)
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{
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bool exit, io;
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struct server_client *const c = server_select(h->server, &io, &exit);
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struct server_client *const c = server_poll(h->server, &io, &exit);
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if (exit)
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{
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@ -242,7 +242,7 @@ int handler_listen(struct handler *const h, const short port)
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}
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else if (!c)
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{
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fprintf(stderr, "%s: server_select failed\n", __func__);
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fprintf(stderr, "%s: server_poll failed\n", __func__);
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return -1;
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}
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95
server.c
95
server.c
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@ -2,9 +2,9 @@
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#include "server.h"
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#include <fcntl.h>
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#include <sys/select.h>
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#include <sys/socket.h>
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#include <netinet/in.h>
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#include <poll.h>
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#include <unistd.h>
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#include <errno.h>
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#include <signal.h>
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@ -170,63 +170,102 @@ static void handle_signal(const int signum)
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do_exit = 1;
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}
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struct server_client *server_select(struct server *const s, bool *const io,
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struct server_client *server_poll(struct server *const s, bool *const io,
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bool *const exit)
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{
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int nfds = -1;
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fd_set rfds, wfds;
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struct server_client *ret = NULL;
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const nfds_t n = s->n + 1;
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struct pollfd *const fds = malloc(n * sizeof *fds);
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if (!fds)
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{
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fprintf(stderr, "%s: malloc(3): %s\n", __func__, strerror(errno));
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goto end;
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}
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struct pollfd *const sfd = &fds[0];
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*io = *exit = false;
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FD_ZERO(&rfds);
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FD_ZERO(&wfds);
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for (size_t i = 0; i < s->n; i++)
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*sfd = (const struct pollfd)
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{
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.fd = s->fd,
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.events = POLLIN
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};
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for (size_t i = 0, j = 1; i < s->n; i++, j++)
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{
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struct pollfd *const p = &fds[j];
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const struct server_client *const c = &s->c[i];
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const int fd = c->fd;
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FD_SET(fd, &rfds);
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*p = (const struct pollfd)
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{
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.fd = fd,
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.events = POLLIN
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};
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if (c->write)
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FD_SET(fd, &wfds);
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if (fd > nfds)
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nfds = fd;
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p->events |= POLLOUT;
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}
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FD_SET(s->fd, &rfds);
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int res;
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if (s->fd > nfds)
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nfds = s->fd;
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again:
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const int res = select(nfds + 1, &rfds, &wfds, NULL, NULL);
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res = poll(fds, n, -1);
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if (res < 0)
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{
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if (do_exit)
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{
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*exit = true;
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else
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fprintf(stderr, "%s: select(2): %s\n", __func__, strerror(errno));
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goto end;
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}
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return NULL;
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switch (errno)
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{
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case EAGAIN:
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/* Fall through. */
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case EINTR:
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goto again;
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default:
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fprintf(stderr, "%s: poll(2): %s\n", __func__, strerror(errno));
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break;
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}
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goto end;
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}
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else if (FD_ISSET(s->fd, &rfds))
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return alloc_client(s);
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for (size_t i = 0; i < s->n; i++)
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else if (!res)
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{
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fprintf(stderr, "%s: poll(2) returned zero\n", __func__);
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goto end;
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}
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if (sfd->revents)
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{
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ret = alloc_client(s);
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goto end;
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}
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for (size_t i = 0, j = 1; i < s->n; i++, j++)
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{
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const struct pollfd *const p = &fds[j];
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struct server_client *const c = &s->c[i];
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if (FD_ISSET(c->fd, &rfds) || FD_ISSET(c->fd, &wfds))
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if (p->revents)
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{
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*io = true;
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return c;
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ret = c;
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goto end;
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}
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}
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fprintf(stderr, "%s: unlisted fd\n", __func__);
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return NULL;
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end:
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free(fds);
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return ret;
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}
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static int init_signals(void)
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2
server.h
2
server.h
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@ -5,7 +5,7 @@
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#include <stddef.h>
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struct server *server_init(unsigned short port);
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struct server_client *server_select(struct server *s, bool *io, bool *exit);
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struct server_client *server_poll(struct server *s, bool *io, bool *exit);
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int server_read(void *buf, size_t n, struct server_client *c);
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int server_write(const void *buf, size_t n, struct server_client *c);
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int server_close(struct server *s);
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