snmp: make use of newer snmp_select_info2() function

When available, it allows to not hit the 1024 FD limit of
snmp_select_info().

diff --git a/m4/snmp.m4 b/m4/snmp.m4
index b820fdb2759856288ab081425fbf0230373299fd..8e4b496fc25e40c7652b4ba40f7928eb84896afa 100644 (file)
--- a/m4/snmp.m4
+++ b/m4/snmp.m4
@@ -53,6 +53,8 @@ int main(void);
 @%:@include <net-snmp/agent/net-snmp-agent-includes.h>
 @%:@include <net-snmp/agent/snmp_vars.h>
             ])
+            dnl Can we use snmp_select_info2?
+            AC_CHECK_FUNCS([snmp_select_info2])
           ],[
             if test x"$with_snmp" = x"yes"; then
               AC_MSG_ERROR([*** no subagent support in net-snmp])

diff --git a/src/daemon/event.c b/src/daemon/event.c
index 50f7977f598f421cf2297fe46317150a2c40611a..65b4be9cb98ce225ad85f3c72b6330aa48a34fdf 100644 (file)
--- a/src/daemon/event.c
+++ b/src/daemon/event.c
@@ -62,6 +62,21 @@ TAILQ_HEAD(ev_l, lldpd_events);
 #include <net-snmp/agent/net-snmp-agent-includes.h>
 #include <net-snmp/agent/snmp_vars.h>
 
+/* Compatibility with older versions of NetSNMP */
+#ifndef HAVE_SNMP_SELECT_INFO2
+# define netsnmp_large_fd_set fd_set
+# define snmp_read2 snmp_read
+# define snmp_select_info2 snmp_select_info
+# define netsnmp_large_fd_set_init(...)
+# define netsnmp_large_fd_set_cleanup(...)
+# define NETSNMP_LARGE_FD_SET FD_SET
+# define NETSNMP_LARGE_FD_CLR FD_CLR
+# define NETSNMP_LARGE_FD_ZERO FD_ZERO
+# define NETSNMP_LARGE_FD_ISSET FD_ISSET
+#else
+# include <net-snmp/library/large_fd_set.h>
+#endif
+
 static void levent_snmp_update(struct lldpd *);
 
 /*
@@ -74,11 +89,12 @@ static void
 levent_snmp_read(evutil_socket_t fd, short what, void *arg)
 {
        struct lldpd *cfg = arg;
-       fd_set fdset;
+       netsnmp_large_fd_set fdset;
        (void)what;
-       FD_ZERO(&fdset);
-       FD_SET(fd, &fdset);
-       snmp_read(&fdset);
+       netsnmp_large_fd_set_init(&fdset, FD_SETSIZE);
+       NETSNMP_LARGE_FD_ZERO(&fdset);
+       NETSNMP_LARGE_FD_SET(fd, &fdset);
+       snmp_read2(&fdset);
        levent_snmp_update(cfg);
 }
 
@@ -148,7 +164,6 @@ levent_snmp_update(struct lldpd *cfg)
 {
        int maxfd = 0;
        int block = 1;
-       fd_set fdset;
        struct timeval timeout;
        static int howmany = 0;
        int added = 0, removed = 0, current = 0;
@@ -158,14 +173,16 @@ levent_snmp_update(struct lldpd *cfg)
           1 to means that we don't request a timeout. snmp_select_info()
           will reset `block` to 0 if it wants us to setup a timeout. In
           this timeout, `snmp_timeout()` should be invoked.
-          
+
           Each FD in `fdset` will need to be watched for reading. If one of
           them become active, `snmp_read()` should be called on it.
        */
-       
-       FD_ZERO(&fdset);
-       snmp_select_info(&maxfd, &fdset, &timeout, &block);
-       
+
+       netsnmp_large_fd_set fdset;
+       netsnmp_large_fd_set_init(&fdset, FD_SETSIZE);
+        NETSNMP_LARGE_FD_ZERO(&fdset);
+       snmp_select_info2(&maxfd, &fdset, &timeout, &block);
+
        /* We need to untrack any event whose FD is not in `fdset`
           anymore */
        for (snmpfd = TAILQ_FIRST(levent_snmp_fds(cfg));
@@ -173,20 +190,20 @@ levent_snmp_update(struct lldpd *cfg)
             snmpfd = snmpfd_next) {
                snmpfd_next = TAILQ_NEXT(snmpfd, next);
                if (event_get_fd(snmpfd->ev) >= maxfd ||
-                   (!FD_ISSET(event_get_fd(snmpfd->ev), &fdset))) {
+                   (!NETSNMP_LARGE_FD_ISSET(event_get_fd(snmpfd->ev), &fdset))) {
                        event_free(snmpfd->ev);
                        TAILQ_REMOVE(levent_snmp_fds(cfg), snmpfd, next);
                        free(snmpfd);
                        removed++;
                } else {
-                       FD_CLR(event_get_fd(snmpfd->ev), &fdset);
+                       NETSNMP_LARGE_FD_CLR(event_get_fd(snmpfd->ev), &fdset);
                        current++;
                }
        }
-       
+
        /* Invariant: FD in `fdset` are not in list of FD */
        for (int fd = 0; fd < maxfd; fd++) {
-               if (FD_ISSET(fd, &fdset)) {
+               if (NETSNMP_LARGE_FD_ISSET(fd, &fdset)) {
                        levent_snmp_add_fd(cfg, fd);
                        added++;
                }
@@ -201,6 +218,8 @@ levent_snmp_update(struct lldpd *cfg)
        /* If needed, handle timeout */
        if (evtimer_add(cfg->g_snmp_timeout, block?NULL:&timeout) == -1)
                log_warnx("event", "unable to schedule timeout function for SNMP");
+
+       netsnmp_large_fd_set_cleanup(&fdset);
 }
 #endif /* USE_SNMP */