Add tcp_log_addrs() function to generate and standardized TCP log line

for use thoughout the tcp subsystem.

It is IPv4 and IPv6 aware creates a line in the following format:

 "TCP: [1.2.3.4]:50332 to [1.2.3.4]:80 tcpflags <RST>"

A "\n" is not included at the end.  The caller is supposed to add
further information after the standard tcp log header.

The function returns a NUL terminated string which the caller has
to free(s, M_TCPLOG) after use.  All memory allocation is done
with M_NOWAIT and the return value may be NULL in memory shortage
situations.

Either struct in_conninfo || (struct tcphdr && (struct ip || struct
ip6_hdr) have to be supplied.

Due to ip[6].h header inclusion limitations and ordering issues the
struct ip and struct ip6_hdr parameters have to be casted and passed
as void * pointers.

tcp_log_addrs(struct in_conninfo *inc, struct tcphdr *th, void *ip4hdr,
    void *ip6hdr)

Usage example:

 struct ip *ip;
 char *tcplog;

 if (tcplog = tcp_log_addrs(NULL, th, (void *)ip, NULL)) {
	log(LOG_DEBUG, "%s; %s: Connection attempt to closed port\n",
	    tcplog, __func__);
	free(s, M_TCPLOG);
 }

1 files changed, 8 insertions, 22 deletions

diff --git a/sys/netinet/tcp_input.c b/sys/netinet/tcp_input.c
index 163b588..02a9c22 100644
--- a/sys/netinet/tcp_input.c
+++ b/sys/netinet/tcp_input.c
@@ -240,7 +240,6 @@ tcp_input(struct mbuf *m, int off0)
 #ifdef INET6
 	struct ip6_hdr *ip6 = NULL;
 	int isipv6;
-	char ip6buf[INET6_ADDRSTRLEN];
 #else
 	const int isipv6 = 0;
 #endif
@@ -481,30 +480,17 @@ findpcb:
 		 */
 		if ((tcp_log_in_vain == 1 && (thflags & TH_SYN)) ||
 		    tcp_log_in_vain == 2) {
-#ifndef INET6
-			char dbuf[4*sizeof "123"], sbuf[4*sizeof "123"];
+			char *s;
+#ifdef INET6
+			s = tcp_log_addrs(NULL, th, (void *)ip, (void *)ip6);
 #else
-			char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2];
-			if (isipv6) {
-				strcpy(dbuf, "[");
-				strcat(dbuf,
-				    ip6_sprintf(ip6buf, &ip6->ip6_dst));
-				strcat(dbuf, "]");
-				strcpy(sbuf, "[");
-				strcat(sbuf,
-				    ip6_sprintf(ip6buf, &ip6->ip6_src));
-				strcat(sbuf, "]");
-			} else
+			s = tcp_log_addrs(NULL, th, (void *)ip, NULL);
 #endif /* INET6 */
-			{
-				strcpy(dbuf, inet_ntoa(ip->ip_dst));
-				strcpy(sbuf, inet_ntoa(ip->ip_src));
+			if (s != NULL) {
+				log(LOG_INFO, "%s; %s: Connection attempt "
+				    "to closed port\n", s, __func__);
+				free(s, M_TCPLOG);
 			}
-			log(LOG_INFO,
-			    "Connection attempt to TCP %s:%d "
-			    "from %s:%d flags:0x%02x\n",
-			    dbuf, ntohs(th->th_dport), sbuf,
-			    ntohs(th->th_sport), thflags);
 		}
 		/*
 		 * When blackholing do not respond with a RST but