- djm@cvs.openbsd.org 2012/04/11 13:16:19

     [channels.c channels.h clientloop.c serverloop.c]
     don't spin in accept() when out of fds (ENFILE/ENFILE) - back off for a
     while; ok deraadt@ markus@

1 files changed, 44 insertions, 8 deletions

diff --git a/channels.c b/channels.c
index e5783b197..cacd2fe55 100644
--- a/channels.c
+++ b/channels.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: channels.c,v 1.316 2012/03/29 23:54:36 dtucker Exp $ */
+/* $OpenBSD: channels.c,v 1.317 2012/04/11 13:16:19 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -311,6 +311,7 @@ channel_new(char *ctype, int type, int rfd, int wfd, int efd,
         c->istate = CHAN_INPUT_OPEN;
         c->flags = 0;
         channel_register_fds(c, rfd, wfd, efd, extusage, nonblock, 0);
+        c->notbefore = 0;
         c->self = found;
         c->type = type;
         c->ctype = ctype;
@@ -1339,6 +1340,8 @@ channel_post_x11_listener(Channel *c, fd_set *readset, fd_set *writeset)
                 }
                 if (newsock < 0) {
                         error("accept: %.100s", strerror(errno));
+                        if (errno == EMFILE || errno == ENFILE)
+                                c->notbefore = time(NULL) + 1;
                         return;
                 }
                 set_nodelay(newsock);
@@ -1482,6 +1485,8 @@ channel_post_port_listener(Channel *c, fd_set *readset, fd_set *writeset)
                 newsock = accept(c->sock, (struct sockaddr *)&addr, &addrlen);
                 if (newsock < 0) {
                         error("accept: %.100s", strerror(errno));
+                        if (errno == EMFILE || errno == ENFILE)
+                                c->notbefore = time(NULL) + 1;
                         return;
                 }
                 set_nodelay(newsock);
@@ -1514,7 +1519,10 @@ channel_post_auth_listener(Channel *c, fd_set *readset, fd_set *writeset)
                 addrlen = sizeof(addr);
                 newsock = accept(c->sock, (struct sockaddr *)&addr, &addrlen);
                 if (newsock < 0) {
-                        error("accept from auth socket: %.100s", strerror(errno));
+                        error("accept from auth socket: %.100s",
+                            strerror(errno));
+                        if (errno == EMFILE || errno == ENFILE)
+                                c->notbefore = time(NULL) + 1;
                         return;
                 }
                 nc = channel_new("accepted auth socket",
@@ -1917,6 +1925,8 @@ channel_post_mux_listener(Channel *c, fd_set *readset, fd_set *writeset)
         if ((newsock = accept(c->sock, (struct sockaddr*)&addr,
             &addrlen)) == -1) {
                 error("%s accept: %s", __func__, strerror(errno));
+                if (errno == EMFILE || errno == ENFILE)
+                        c->notbefore = time(NULL) + 1;
                 return;
         }
 
@@ -2067,16 +2077,21 @@ channel_garbage_collect(Channel *c)
 }
 
 static void
-channel_handler(chan_fn *ftab[], fd_set *readset, fd_set *writeset)
+channel_handler(chan_fn *ftab[], fd_set *readset, fd_set *writeset,
+    time_t *unpause_secs)
 {
         static int did_init = 0;
         u_int i, oalloc;
         Channel *c;
+        time_t now;
 
         if (!did_init) {
                 channel_handler_init();
                 did_init = 1;
         }
+        now = time(NULL);
+        if (unpause_secs != NULL)
+                *unpause_secs = 0;
         for (i = 0, oalloc = channels_alloc; i < oalloc; i++) {
                 c = channels[i];
                 if (c == NULL)
@@ -2087,10 +2102,30 @@ channel_handler(chan_fn *ftab[], fd_set *readset, fd_set *writeset)
                         else
                                 continue;
                 }
-                if (ftab[c->type] != NULL)
-                        (*ftab[c->type])(c, readset, writeset);
+                if (ftab[c->type] != NULL) {
+                        /*
+                         * Run handlers that are not paused.
+                         */
+                        if (c->notbefore <= now)
+                                (*ftab[c->type])(c, readset, writeset);
+                        else if (unpause_secs != NULL) {
+                                /*
+                                 * Collect the time that the earliest
+                                 * channel comes off pause.
+                                 */
+                                debug3("%s: chan %d: skip for %d more seconds",
+                                    __func__, c->self,
+                                    (int)(c->notbefore - now));
+                                if (*unpause_secs == 0 ||
+                                    (c->notbefore - now) < *unpause_secs)
+                                        *unpause_secs = c->notbefore - now;
+                        }
+                }
                 channel_garbage_collect(c);
         }
+        if (unpause_secs != NULL && *unpause_secs != 0)
+                debug3("%s: first channel unpauses in %d seconds",
+                    __func__, (int)*unpause_secs);
 }
 
 /*
@@ -2099,7 +2134,7 @@ channel_handler(chan_fn *ftab[], fd_set *readset, fd_set *writeset)
  */
 void
 channel_prepare_select(fd_set **readsetp, fd_set **writesetp, int *maxfdp,
-    u_int *nallocp, int rekeying)
+    u_int *nallocp, int *minwait_secs, int rekeying)
 {
         u_int n, sz, nfdset;
 
@@ -2122,7 +2157,8 @@ channel_prepare_select(fd_set **readsetp, fd_set **writesetp, int *maxfdp,
         memset(*writesetp, 0, sz);
 
         if (!rekeying)
-                channel_handler(channel_pre, *readsetp, *writesetp);
+                channel_handler(channel_pre, *readsetp, *writesetp,
+                    minwait_secs);
 }
 
 /*
@@ -2132,7 +2168,7 @@ channel_prepare_select(fd_set **readsetp, fd_set **writesetp, int *maxfdp,
 void
 channel_after_select(fd_set *readset, fd_set *writeset)
 {
-        channel_handler(channel_post, readset, writeset);
+        channel_handler(channel_post, readset, writeset, NULL);
 }