Renumber IPPROTO_DIVERT out of the range of valid IP protocol numbers.

This allows socket() to return an error when the kernel is not built
with IPDIVERT, and doesn't prevent future applications from using the
"borrowed" IP protocol number.  The sysctl net.inet.raw.olddiverterror
controls whether opening a socket with the "borrowed" IP protocol
fails with an accompanying kernel printf; this code should last only a
couple of releases.

Approved by:	re

3 files changed, 19 insertions, 4 deletions

diff --git a/sys/netinet/in.h b/sys/netinet/in.h
index 09fd395..c974bc5 100644
--- a/sys/netinet/in.h
+++ b/sys/netinet/in.h
@@ -236,13 +236,16 @@ __END_DECLS
 #define	IPPROTO_PIM		103		/* Protocol Independent Mcast */
 #define	IPPROTO_PGM		113		/* PGM */
 /* 255: Reserved */
-/* BSD Private, local use, namespace incursion */
-#define	IPPROTO_DIVERT		254		/* divert pseudo-protocol */
+/* BSD Private, local use, namespace incursion, no longer used */
+#define	IPPROTO_OLD_DIVERT	254		/* OLD divert pseudo-proto */
 #define	IPPROTO_MAX		256
 
 /* last return value of *_input(), meaning "all job for this pkt is done".  */
 #define	IPPROTO_DONE		257
 
+/* Only used internally, so can be outside the range of valid IP protocols. */
+#define	IPPROTO_DIVERT		258		/* divert pseudo-protocol */
+
 /*
  * Local port number conventions:
  *
diff --git a/sys/netinet/ip_divert.c b/sys/netinet/ip_divert.c
index 808819d..9082733 100644
--- a/sys/netinet/ip_divert.c
+++ b/sys/netinet/ip_divert.c
@@ -136,8 +136,8 @@ div_init(void)
 }
 
 /*
- * IPPROTO_DIVERT is not a real IP protocol; don't allow any packets
- * with that protocol number to enter the system from the outside.
+ * IPPROTO_DIVERT is not in the real IP protocol number space; this
+ * function should never be called.  Just in case, drop any packets.
  */
 void
 div_input(struct mbuf *m, int off)
diff --git a/sys/netinet/raw_ip.c b/sys/netinet/raw_ip.c
index 97dabef..f435d97 100644
--- a/sys/netinet/raw_ip.c
+++ b/sys/netinet/raw_ip.c
@@ -493,11 +493,14 @@ rip_ctlinput(cmd, sa, vip)
 
 u_long	rip_sendspace = RIPSNDQ;
 u_long	rip_recvspace = RIPRCVQ;
+int	rip_olddiverterror = 1;
 
 SYSCTL_INT(_net_inet_raw, OID_AUTO, maxdgram, CTLFLAG_RW,
     &rip_sendspace, 0, "Maximum outgoing raw IP datagram size");
 SYSCTL_INT(_net_inet_raw, OID_AUTO, recvspace, CTLFLAG_RW,
     &rip_recvspace, 0, "Maximum incoming raw IP datagram size");
+SYSCTL_INT(_net_inet_raw, OID_AUTO, olddiverterror, CTLFLAG_RW,
+    &rip_olddiverterror, 0, "Return an error when creating an 'old' DIVERT socket");
 
 static int
 rip_attach(struct socket *so, int proto, struct thread *td)
@@ -511,6 +514,15 @@ rip_attach(struct socket *so, int proto, struct thread *td)
 	if (td && (error = suser(td)) != 0)
 		return error;
 
+	if (proto >= IPPROTO_MAX || proto < 0)
+		return EPROTONOSUPPORT;
+
+	/* To be removed before 5.2 */
+	if (rip_olddiverterror && proto == IPPROTO_OLD_DIVERT) {
+		printf("Old IPDIVERT program needs to be recompiled, or new IP proto 254 user needs sysctl net.inet.raw.olddiverterror=0\n");
+		return EPROTONOSUPPORT;
+	}
+
 	error = soreserve(so, rip_sendspace, rip_recvspace);
 	if (error)
 		return error;