From bc598c23dc6141d69167a8bbfbd5f656cf5ccd2c Mon Sep 17 00:00:00 2001
From: Vincent Bernat <bernat@luffy.cx>
Date: Fri, 12 Mar 2010 12:03:24 +0100
Subject: [PATCH] Retrieve FD_SETSIZE in a sane environment.

Since we import linux/if.h, in some environment, we may end up
importing kernel FD_SETSIZE that may be inappropriate (too large). For
example, on Sarge systems, FD_SETSIZE becomes 8192 instead of 1024 but
FD_ISSET is unable to handle this size.
---
 configure.ac     |  1 +
 m4/fdsetsize.m4  | 32 ++++++++++++++++++++++++++++++++
 src/interfaces.c |  2 +-
 src/lldpd.c      | 12 ++++++++----
 4 files changed, 42 insertions(+), 5 deletions(-)
 create mode 100644 m4/fdsetsize.m4

diff --git a/configure.ac b/configure.ac
index ae684b3f..70510541 100644
--- a/configure.ac
+++ b/configure.ac
@@ -161,6 +161,7 @@ AC_TYPE_UINT16_T
 AC_TYPE_UINT32_T
 AC_TYPE_UINT8_T
 lldp_CHECK___PROGNAME
+lldp_CHECK_FD_SETSIZE
 
 # Checks for library functions.
 AC_FUNC_CHOWN
diff --git a/m4/fdsetsize.m4 b/m4/fdsetsize.m4
new file mode 100644
index 00000000..74197f84
--- /dev/null
+++ b/m4/fdsetsize.m4
@@ -0,0 +1,32 @@
+#
+# lldp_CHECK_FD_SETSIZE
+#
+AC_DEFUN([lldp_CHECK_FD_SETSIZE],[
+  AC_CACHE_CHECK([real value of FD_SETSIZE], lldp_cv_check_fd_setsize, [
+    AC_RUN_IFELSE([
+       AC_LANG_PROGRAM(
+        [
+@%:@include <stdio.h>
+@%:@include <sys/select.h>
+@%:@include <sys/time.h>
+@%:@include <sys/types.h>
+@%:@include <unistd.h>
+	],
+	[
+	FILE *fd;
+	if ((fd = fopen("conftest.out", "w")) == NULL) {
+	   printf("Unable to create file conftest.out");
+	   return 1;
+        }
+	fprintf(fd, "%d\n", FD_SETSIZE);
+	fclose(fd);
+	])],
+       [ lldp_cv_check_fd_setsize=`cat conftest.out` ],
+       [ lldp_cv_check_fd_setsize="no" ])])
+  if test x"$lldp_cv_check_fd_setsize" = x"no"; then
+     AC_DEFINE([LLDPD_FD_SETSIZE], [FD_SETSIZE], [FD_SETSIZE for select()])
+  else
+     AC_DEFINE_UNQUOTED([LLDPD_FD_SETSIZE], $lldp_cv_check_fd_setsize,
+               [FD_SETSIZE for select()])
+  fi
+])
diff --git a/src/interfaces.c b/src/interfaces.c
index 18a1e302..5192ee1f 100644
--- a/src/interfaces.c
+++ b/src/interfaces.c
@@ -602,7 +602,7 @@ static void
 iface_fds_close(struct lldpd *cfg, struct lldpd_hardware *hardware)
 {
 	int i;
-	for (i=0; i < FD_SETSIZE; i++)
+	for (i=0; i < LLDPD_FD_SETSIZE; i++)
 		if (FD_ISSET(i, &hardware->h_recvfds)) {
 			FD_CLR(i, &hardware->h_recvfds);
 			close(i);
diff --git a/src/lldpd.c b/src/lldpd.c
index 6e7b974e..98f27708 100644
--- a/src/lldpd.c
+++ b/src/lldpd.c
@@ -33,6 +33,10 @@
 #include <arpa/inet.h>
 #include <net/if_arp.h>
 
+#if LLDPD_FD_SETSIZE != FD_SETSIZE
+# warning "FD_SETSIZE is set to an inconsistent value."
+#endif
+
 #ifdef USE_SNMP
 #include <net-snmp/net-snmp-config.h>
 #include <net-snmp/net-snmp-includes.h>
@@ -240,7 +244,7 @@ lldpd_hardware_cleanup(struct lldpd *cfg, struct lldpd_hardware *hardware)
 		hardware->h_ops->cleanup(cfg, hardware);
 	else {
 		free(hardware->h_data);
-		for (i=0; i < FD_SETSIZE; i++)
+		for (i=0; i < LLDPD_FD_SETSIZE; i++)
 			if (FD_ISSET(i, &hardware->h_recvfds))
 				close(i);
 		if (hardware->h_sendfd) close(hardware->h_sendfd);
@@ -482,7 +486,7 @@ lldpd_recv_all(struct lldpd *cfg)
 				continue;
 			/* This is quite expensive but we don't rely on internal
 			 * structure of fd_set. */
-			for (n = 0; n < FD_SETSIZE; n++)
+			for (n = 0; n < LLDPD_FD_SETSIZE; n++)
 				if (FD_ISSET(n, &hardware->h_recvfds)) {
 					FD_SET(n, &rfds);
 					if (nfds < n)
@@ -520,10 +524,10 @@ lldpd_recv_all(struct lldpd *cfg)
 		}
 #endif /* USE_SNMP */
 		TAILQ_FOREACH(hardware, &cfg->g_hardware, h_entries) {
-			for (n = 0; n < FD_SETSIZE; n++)
+			for (n = 0; n < LLDPD_FD_SETSIZE; n++)
 				if ((FD_ISSET(n, &hardware->h_recvfds)) &&
 				    (FD_ISSET(n, &rfds))) break;
-			if (n == FD_SETSIZE) continue;
+			if (n == LLDPD_FD_SETSIZE) continue;
 			if ((buffer = (char *)malloc(
 					hardware->h_mtu)) == NULL) {
 				LLOG_WARN("failed to alloc reception buffer");
-- 
2.39.5