Set the SO_REUSEADDR flag on listening sockets.

This way we can have a global listen statement, but add an additional
listener on with different flags on specific interfaces (e.g. allow
snmpv2c on localhost for easier testing)

OK sthen@

diff --git a/usr.sbin/snmpd/snmpd.c b/usr.sbin/snmpd/snmpd.c
index 750ffd7..bc32cc9 100644 (file)
--- a/usr.sbin/snmpd/snmpd.c
+++ b/usr.sbin/snmpd/snmpd.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: snmpd.c,v 1.45 2021/08/09 18:14:53 martijn Exp $      */
+/*     $OpenBSD: snmpd.c,v 1.46 2021/08/10 06:52:03 martijn Exp $      */
 
 /*
  * Copyright (c) 2007, 2008, 2012 Reyk Floeter <reyk@openbsd.org>
@@ -312,8 +312,22 @@ snmpd_dispatch_snmpe(int fd, struct privsep_proc *p, struct imsg *imsg)
 int
 snmpd_socket_af(struct sockaddr_storage *ss, int type)
 {
-       return socket(ss->ss_family, (type == SOCK_STREAM ?
+       int fd, serrno;
+       const int enable = 1;
+
+       fd = socket(ss->ss_family, (type == SOCK_STREAM ?
            SOCK_STREAM | SOCK_NONBLOCK : SOCK_DGRAM) | SOCK_CLOEXEC, 0);
+       if (fd == -1)
+               return -1;
+
+       if (setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &enable,
+           sizeof(enable)) == -1) {
+               serrno = errno;
+               close(fd);
+               errno = serrno;
+               return -1;
+       }
+       return fd;
 }
 
 u_long