From: Alexander Bluhm <bluhm@openbsd.org>
Subject: tcp debug mutex
To: tech@openbsd.org
Date: Wed, 10 Apr 2024 21:05:50 +0200

Hi,

Protect the global variables in TCP debug code with global mutex.
Add a missing include and also fix the -Wunused-but-set-variable
warning.

ok?

bluhm

Index: netinet/tcp_debug.c
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/netinet/tcp_debug.c,v
diff -u -p -r1.31 tcp_debug.c
--- netinet/tcp_debug.c	11 Jan 2024 13:49:49 -0000	1.31
+++ netinet/tcp_debug.c	10 Apr 2024 18:53:38 -0000
@@ -79,6 +79,7 @@
 #include <sys/param.h>
 #include <sys/systm.h>
 #include <sys/mbuf.h>
+#include <sys/mutex.h>
 #include <sys/socket.h>
 
 #include <net/route.h>
@@ -99,20 +100,32 @@
 #endif /* INET6 */
 
 #ifdef TCPDEBUG
+#include <sys/protosw.h>
+#endif
+
+/*
+ *  Locks used to protect struct members in this file:
+ *	D	TCP debug global mutex
+ */
+
+struct mutex tcp_debug_mtx = MUTEX_INITIALIZER(IPL_SOFTNET);
+
+#ifdef TCPDEBUG
 int	tcpconsdebug = 0;
 #endif
 
-struct	tcp_debug tcp_debug[TCP_NDEBUG];
-int	tcp_debx;
+struct	tcp_debug tcp_debug[TCP_NDEBUG];	/* [D] */
+int	tcp_debx;				/* [D] */
 
 /*
  * Tcp debug routines
  */
 void
-tcp_trace(short act, short ostate, struct tcpcb *tp, struct tcpcb *otp,
+tcp_trace_locked(short act, short ostate, struct tcpcb *tp, struct tcpcb *otp,
     caddr_t headers, int req, int len)
 {
 #ifdef TCPDEBUG
+	struct tcphdr *th;
 	tcp_seq seq, ack;
 	int flags;
 #endif
@@ -120,7 +133,6 @@ tcp_trace(short act, short ostate, struc
 	struct tcp_debug *td = &tcp_debug[tcp_debx++];
 	struct tcpiphdr *ti = (struct tcpiphdr *)headers;
 	struct tcpipv6hdr *ti6 = (struct tcpipv6hdr *)headers;
-	struct tcphdr *th;
 
 	if (tcp_debx == TCP_NDEBUG)
 		tcp_debx = 0;
@@ -153,13 +165,17 @@ tcp_trace(short act, short ostate, struc
 		switch (pf) {
 #ifdef INET6
 		case PF_INET6:
+#ifdef TCPDEBUG
 			th = &ti6->ti6_t;
+#endif
 			td->td_ti6 = *ti6;
 			td->td_ti6.ti6_plen = len;
 			break;
 #endif /* INET6 */
 		case PF_INET:
+#ifdef TCPDEBUG
 			th = &ti->ti_t;
+#endif
 			td->td_ti = *ti;
 			td->td_ti.ti_len = len;
 			break;
@@ -225,4 +241,13 @@ tcp_trace(short act, short ostate, struc
 	printf("\tsnd_(wl1,wl2,wnd) (%x,%x,%lx)\n",
 	    tp->snd_wl1, tp->snd_wl2, tp->snd_wnd);
 #endif /* TCPDEBUG */
+}
+
+void
+tcp_trace(short act, short ostate, struct tcpcb *tp, struct tcpcb *otp,
+    caddr_t headers, int req, int len)
+{
+	mtx_enter(&tcp_debug_mtx);
+	tcp_trace_locked(act, ostate, tp, otp, headers, req, len);
+	mtx_leave(&tcp_debug_mtx);
 }