Fix IP_SENDSRCADDR semantics.

 * To use this option with a UDP socket, it must be bound to a local port,
   and INADDR_ANY, to disallow possible collisions with existing udp inpcbs
   bound to the same port on other interfaces at send time.

 * If the socket is bound to INADDR_ANY, specifying IP_SENDSRCADDR with
   INADDR_ANY will be rejected as it is ambiguous.

 * If the socket is bound to an address other than INADDR_ANY, specifying
   IP_SENDSRCADDR with INADDR_ANY will be disallowed by in_pcbbind_setup().

Reviewed by:	silence on -net
Tested with:	src/tools/regression/netinet/ipbroadcast
MFC after:	4 days

1 files changed, 11 insertions, 4 deletions

diff --git a/sys/netinet/udp_usrreq.c b/sys/netinet/udp_usrreq.c
index 2743cf7..0966f2e 100644
--- a/sys/netinet/udp_usrreq.c
+++ b/sys/netinet/udp_usrreq.c
@@ -747,7 +747,7 @@ udp_output(struct inpcb *inp, struct mbuf *m, struct sockaddr *addr,
 		return (EMSGSIZE);
 	}
 
-	src.sin_addr.s_addr = INADDR_ANY;
+	src.sin_family = 0;
 	if (control != NULL) {
 		/*
 		 * XXX: Currently, we assume all the optional information is
@@ -797,7 +797,7 @@ udp_output(struct inpcb *inp, struct mbuf *m, struct sockaddr *addr,
 		return (error);
 	}
 
-	if (src.sin_addr.s_addr != INADDR_ANY || addr != NULL) {
+	if (src.sin_family == AF_INET || addr != NULL) {
 		INP_INFO_WLOCK(&udbinfo);
 		unlock_udbinfo = 1;
 	} else
@@ -808,10 +808,17 @@ udp_output(struct inpcb *inp, struct mbuf *m, struct sockaddr *addr,
 	mac_create_mbuf_from_inpcb(inp, m);
 #endif
 
+	/*
+	 * If the IP_SENDSRCADDR control message was specified, override the
+	 * source address for this datagram. Its use is invalidated if the
+	 * address thus specified is incomplete or clobbers other inpcbs.
+	 */
 	laddr = inp->inp_laddr;
 	lport = inp->inp_lport;
-	if (src.sin_addr.s_addr != INADDR_ANY) {
-		if (lport == 0) {
+	if (src.sin_family == AF_INET) {
+		if ((lport == 0) ||
+		    (laddr.s_addr == INADDR_ANY &&
+		     src.sin_addr.s_addr == INADDR_ANY)) {
 			error = EINVAL;
 			goto release;
 		}