Attachment 2818 Details for Bug 2576 – avoid busy-wait on per-process fd exhaustion

[patch] avoid busy-wait on per-process fd exhaustion

bz2576.diff (text/plain), 4.19 KB, created by Damien Miller on 2016-05-31 11:45:17 AEST

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Creator: Damien Miller

Created: 2016-05-31 11:45:17 AEST

Size: 4.19 KB

patch

obsolete

>diff --git a/ssh-agent.c b/ssh-agent.c
>index 1dc0cfa..32a7c86 100644
>--- a/ssh-agent.c
>+++ b/ssh-agent.c
>@@ -967,17 +967,19 @@ new_socket(sock_type type, int fd)
> 
> static int
> prepare_select(fd_set **fdrp, fd_set **fdwp, int *fdl, u_int *nallocp,
>-    struct timeval **tvpp)
>+    u_int *livep, u_int live_max, struct timeval **tvpp)
> {
> 	u_int i, sz;
> 	int n = 0;
> 	static struct timeval tv;
> 	time_t deadline;
> 
>-	for (i = 0; i < sockets_alloc; i++) {
>+	for (i = *livep = 0; i < sockets_alloc; i++) {
> 		switch (sockets[i].type) {
>-		case AUTH_SOCKET:
> 		case AUTH_CONNECTION:
>+			(*livep)++;
>+			/* FALLTHROUGH */
>+		case AUTH_SOCKET:
> 			n = MAX(n, sockets[i].fd);
> 			break;
> 		case AUTH_UNUSED:
>@@ -988,6 +990,9 @@ prepare_select(fd_set **fdrp, fd_set **fdwp, int *fdl, u_int *nallocp,
> 		}
> 	}
> 
>+	if (*livep >= live_max)
>+		debug("%s: over fd limit %u >= %u", __func__, *livep, live_max);
>+
> 	sz = howmany(n+1, NFDBITS) * sizeof(fd_mask);
> 	if (*fdrp == NULL || sz > *nallocp) {
> 		free(*fdrp);
>@@ -1005,6 +1010,13 @@ prepare_select(fd_set **fdrp, fd_set **fdwp, int *fdl, u_int *nallocp,
> 	for (i = 0; i < sockets_alloc; i++) {
> 		switch (sockets[i].type) {
> 		case AUTH_SOCKET:
>+			/*
>+			 * If we are over our FD limit then ignore
>+			 * new connections until some close.
>+			 */
>+			if (*livep >= live_max)
>+				break;
>+			/* FALLTHROUGH */
> 		case AUTH_CONNECTION:
> 			FD_SET(sockets[i].fd, *fdrp);
> 			if (sshbuf_len(sockets[i].output) > 0)
>@@ -1029,7 +1041,7 @@ prepare_select(fd_set **fdrp, fd_set **fdwp, int *fdl, u_int *nallocp,
> }
> 
> static void
>-after_select(fd_set *readset, fd_set *writeset)
>+after_select(fd_set *readset, fd_set *writeset, u_int *livep, u_int live_max)
> {
> 	struct sockaddr_un sunaddr;
> 	socklen_t slen;
>@@ -1046,6 +1058,10 @@ after_select(fd_set *readset, fd_set *writeset)
> 		case AUTH_SOCKET:
> 			if (FD_ISSET(sockets[i].fd, readset)) {
> 				slen = sizeof(sunaddr);
>+				if (*livep >= live_max) {
>+					debug("over FD limit; skipping accept");
>+					break;
>+				}
> 				sock = accept(sockets[i].fd,
> 				    (struct sockaddr *)&sunaddr, &slen);
> 				if (sock < 0) {
>@@ -1053,6 +1069,7 @@ after_select(fd_set *readset, fd_set *writeset)
> 					    strerror(errno));
> 					break;
> 				}
>+				(*livep)++;
> 				if (getpeereid(sock, &euid, &egid) < 0) {
> 					error("getpeereid %d failed: %s",
> 					    sock, strerror(errno));
>@@ -1080,6 +1097,7 @@ after_select(fd_set *readset, fd_set *writeset)
> 					continue;
> 				if (len <= 0) {
> 					close_socket(&sockets[i]);
>+					(*livep)--;
> 					break;
> 				}
> 				if ((r = sshbuf_consume(sockets[i].output,
>@@ -1094,6 +1112,7 @@ after_select(fd_set *readset, fd_set *writeset)
> 					continue;
> 				if (len <= 0) {
> 					close_socket(&sockets[i]);
>+					(*livep)--;
> 					break;
> 				}
> 				if ((r = sshbuf_put(sockets[i].input,
>@@ -1179,6 +1198,7 @@ main(int ac, char **av)
> 	struct timeval *tvp = NULL;
> 	size_t len;
> 	mode_t prev_mask;
>+	u_int live = 0, live_max;
> 
> 	ssh_malloc_init();	/* must be called before any mallocs */
> 	/* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
>@@ -1275,6 +1295,17 @@ main(int ac, char **av)
> 	}
> 	parent_pid = getpid();
> 
>+	if (getrlimit(RLIMIT_NOFILE, &rlim) == -1)
>+		fatal("%s: getrlimit: %s", __progname, strerror(errno));
>+	/*
>+	 * Minimum file descriptors:
>+	 * stdio (3) + listener (1) + syslog (1 maybe) + connection (1).
>+	 */
>+	if (rlim.rlim_cur < (3+1+1+1))
>+		fatal("%s: file descriptior rlimit %ld too low",
>+		    __progname, (long)rlim.rlim_cur);
>+	live_max = rlim.rlim_cur - (3+1+1);
>+
> 	if (agentsocket == NULL) {
> 		/* Create private directory for agent socket */
> 		mktemp_proto(socket_dir, sizeof(socket_dir));
>@@ -1390,7 +1421,8 @@ skip:
> 		fatal("%s: pledge: %s", __progname, strerror(errno));
> 
> 	while (1) {
>-		prepare_select(&readsetp, &writesetp, &max_fd, &nalloc, &tvp);
>+		prepare_select(&readsetp, &writesetp, &max_fd,
>+		    &nalloc, &live, live_max, &tvp);
> 		result = select(max_fd + 1, readsetp, writesetp, NULL, tvp);
> 		saved_errno = errno;
> 		if (parent_alive_interval != 0)
>@@ -1401,7 +1433,7 @@ skip:
> 				continue;
> 			fatal("select: %s", strerror(saved_errno));
> 		} else if (result > 0)
>-			after_select(readsetp, writesetp);
>+			after_select(readsetp, writesetp, &live, live_max);
> 	}
> 	/* NOTREACHED */
> }

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