Is there a particular reason why there is no option to log
"unsolicited" udp packets?

/Johan

--- netinet/udp_var.h	2002/06/30 22:40:38	1.19
+++ netinet/udp_var.h	2002/12/01 17:31:53
@@ -75,13 +75,15 @@
 #define	UDPCTL_CHECKSUM		1	/* checksum UDP packets */
 #define	UDPCTL_SENDSPACE	2	/* default send buffer */
 #define	UDPCTL_RECVSPACE	3	/* default recv buffer */
-#define	UDPCTL_MAXID		4
+#define	UDPCTL_LOG_REFUSED	4	/* log refused connections */
+#define	UDPCTL_MAXID		5
 
 #define UDPCTL_NAMES { \
 	{ 0, 0 }, \
 	{ "checksum", CTLTYPE_INT }, \
 	{ "sendspace", CTLTYPE_INT }, \
 	{ "recvspace", CTLTYPE_INT }, \
+	{ "log_refused", CTLTYPE_INT }, \
 }
 
 #ifdef _KERNEL
--- netinet/udp_usrreq.c	2002/08/14 00:23:36	1.96
+++ netinet/udp_usrreq.c	2002/12/01 17:31:53
@@ -79,6 +79,7 @@
 #include <sys/socket.h>
 #include <sys/socketvar.h>
 #include <sys/errno.h>
+#include <sys/syslog.h>
 #include <sys/stat.h>
 #include <sys/systm.h>
 #include <sys/proc.h>
@@ -200,6 +201,52 @@
 }
 
 #ifdef INET
+static void
+udp4_log_refused(const struct ip *ip, const struct udphdr *uh)
+{
+	char src[4*sizeof "123"];
+	char dst[4*sizeof "123"];
+
+	if (ip) {
+		strcpy(src, inet_ntoa(ip->ip_src));
+		strcpy(dst, inet_ntoa(ip->ip_dst));
+	}
+	else {
+		strcpy(src, "(unknown)");
+		strcpy(dst, "(unknown)");
+	}
+	log(LOG_INFO,
+	    "Unhandled UDP packet to %s:%d from %s:%d\n",
+	    dst, ntohs(uh->uh_dport),
+	    src, ntohs(uh->uh_sport));
+}
+#endif
+
+#ifdef INET6
+static void
+udp6_log_refused(const struct ip6_hdr *ip6, const struct udphdr *uh)
+{
+	char src[INET6_ADDRSTRLEN];
+	char dst[INET6_ADDRSTRLEN];
+
+	if (ip6) {
+		strcpy(src, ip6_sprintf(&ip6->ip6_src));
+		strcpy(dst, ip6_sprintf(&ip6->ip6_dst));
+	}
+	else {
+		strcpy(src, "(unknown v6)");
+		strcpy(dst, "(unknown v6)");
+	}
+	log(LOG_INFO,
+	    "Unhandled UDP packet to [%s]:%d from [%s]:%d\n",
+	    dst, ntohs(uh->uh_dport),
+	    src, ntohs(uh->uh_sport));
+}
+#endif
+
+int udp_log_refused;
+
+#ifdef INET
 void
 #if __STDC__
 udp_input(struct mbuf *m, ...)
@@ -367,6 +414,8 @@
 			goto bad;
 		}
 #endif
+		if (udp_log_refused)
+		    udp4_log_refused(ip, uh);
 		icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_PORT, 0, 0);
 		m = NULL;
 	}
@@ -479,6 +528,8 @@
 			goto bad;
 		}
 		udp6stat.udp6s_noport++;
+		if (udp_log_refused)
+		    udp6_log_refused(ip, uh);
 		icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOPORT, 0);
 		m = NULL;
 	}
@@ -1143,6 +1194,9 @@
 	case UDPCTL_RECVSPACE:
 		return (sysctl_int(oldp, oldlenp, newp, newlen,
 		    &udp_recvspace));
+	case UDPCTL_LOG_REFUSED:
+		return (sysctl_int(oldp, oldlenp, newp, newlen,
+		    &udp_log_refused));
 	default:
 		return (ENOPROTOOPT);
 	}