[MINOR] frontend: only check for monitor-net rules if LI_O_CHK_MONNET is set

We can disable the monitor-net rules on a listener if this flag is not
set in the listener's options. This will be useful when we don't want
to check that fe->addr is set or not for non-TCP frontends.

include/types/protocols.h

@@ -73,6 +73,7 @@
 #define LI_O_NOQUICKACK	0x0004	/* disable quick ack of immediate data (linux) */
 #define LI_O_DEF_ACCEPT	0x0008	/* wait up to 1 second for data before accepting */
 #define LI_O_TCP_RULES  0x0010  /* run TCP rules checks on the incoming connection */
+#define LI_O_CHK_MONNET 0x0020  /* check the source against a monitor-net rule */
 
 /* The listener will be directly referenced by the fdtab[] which holds its
  * socket. The listener provides the protocol-specific accept() function to

src/cfgparse.c

@@ -5359,6 +5359,9 @@ int check_config_validity()
 			if (!LIST_ISEMPTY(&curproxy->tcp_req.l4_rules))
 				listener->options |= LI_O_TCP_RULES;
 
+			if (curproxy->mon_mask.s_addr)
+				listener->options |= LI_O_CHK_MONNET;
+
 			/* smart accept mode is automatic in HTTP mode */
 			if ((curproxy->options2 & PR_O2_SMARTACC) ||
 			    (curproxy->mode == PR_MODE_HTTP &&

src/frontend.c

@@ -79,7 +79,7 @@ int frontend_accept(struct listener *l, int cfd, struct sockaddr_storage *addr)
 	/* if this session comes from a known monitoring system, we want to ignore
 	 * it as soon as possible, which means closing it immediately for TCP.
 	 */
-	if (unlikely(p->mon_mask.s_addr &&
+	if (unlikely((l->options & LI_O_CHK_MONNET) &&
 		     addr->ss_family == AF_INET &&
 		     (((struct sockaddr_in *)addr)->sin_addr.s_addr & p->mon_mask.s_addr) == p->mon_net.s_addr)) {
 		if (p->mode == PR_MODE_TCP) {