Provide a sysctl to toggle reporting of TCP debug logging:

 sys.net.inet.tcp.log_debug = 1

It defaults to enabled for the moment and is to be turned off for
the next release like other diagnostics from development branches.

It is important to note that sysctl sys.net.inet.tcp.log_in_vain
uses the same logging function as log_debug.  Enabling of the former
also causes the latter to engage, but not vice versa.

Use consistent terminology in tcp log messages:

 "ignored" means a segment contains invalid flags/information and
   is dropped without changing state or issuing a reply.

 "rejected" means a segments contains invalid flags/information but
   is causing a reply (usually RST) and may cause a state change.

Approved by:	re (rwatson)

1 files changed, 8 insertions, 0 deletions

diff --git a/sys/netinet/tcp_subr.c b/sys/netinet/tcp_subr.c
index 16d4d92..963563d 100644
--- a/sys/netinet/tcp_subr.c
+++ b/sys/netinet/tcp_subr.c
@@ -133,6 +133,10 @@ int	tcp_do_rfc1323 = 1;
 SYSCTL_INT(_net_inet_tcp, TCPCTL_DO_RFC1323, rfc1323, CTLFLAG_RW,
     &tcp_do_rfc1323, 0, "Enable rfc1323 (high performance TCP) extensions");
 
+static int	tcp_log_debug = 1;
+SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_debug, CTLFLAG_RW,
+    &tcp_log_debug, 0, "Log errors caused by incoming TCP segments");
+
 static int	tcp_tcbhashsize = 0;
 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tcbhashsize, CTLFLAG_RDTUN,
     &tcp_tcbhashsize, 0, "Size of TCP control-block hashtable");
@@ -2094,6 +2098,10 @@ tcp_log_addrs(struct in_conninfo *inc, struct tcphdr *th, void *ip4hdr,
 	    2 * INET_ADDRSTRLEN;
 #endif /* INET6 */
 
+	/* Is logging enabled? */
+	if (tcp_log_debug == 0 && tcp_log_in_vain == 0)
+		return (NULL);
+
 	s = malloc(size, M_TCPLOG, M_ZERO|M_NOWAIT);
 	if (s == NULL)
 		return (NULL);