net: remove dom_ifmtu

It is a remnant of a network stack design that was supposed to support
multiple network protocols.  Today it is clear that we are left with IPv4
and IPv6 only.  Only IPv6 may have an MTU different to the interface MTU.

Author: glebius

sys/net/if.c

@@ -4467,19 +4467,6 @@ if_getmtu(const if_t ifp)
 	return (ifp->if_mtu);
 }
 
-int
-if_getmtu_family(const if_t ifp, int family)
-{
-	struct domain *dp;
-
-	SLIST_FOREACH(dp, &domains, dom_next) {
-		if (dp->dom_family == family && dp->dom_ifmtu != NULL)
-			return (dp->dom_ifmtu(ifp));
-	}
-
-	return (ifp->if_mtu);
-}
-
 void
 if_setppromisc(if_t ifp, bool ppromisc)
 {

sys/net/if_var.h

@@ -620,7 +620,6 @@ const uint8_t *if_getbroadcastaddr(const if_t ifp);
 void if_setbroadcastaddr(if_t ifp, const uint8_t *);
 int if_setmtu(if_t ifp, int mtu);
 int if_getmtu(const if_t ifp);
-int if_getmtu_family(const if_t ifp, int family);
 void if_notifymtu(if_t ifp);
 void if_setppromisc(const if_t ifp, bool ppromisc);
 int if_setflagbits(if_t ifp, int set, int clear);

sys/net/route.c

@@ -508,26 +508,29 @@ rt_getifa_fib(struct rt_addrinfo *info, u_int fibnum)
 	return (error);
 }
 
+/*
+ * Try to update rt_mtu for all routes using this interface.  Unfortunately the
+ * only way to do this is to traverse all routing tables in all fibs.
+ */
 void
 rt_updatemtu(struct ifnet *ifp)
 {
 	struct rib_head *rnh;
-	int mtu;
-	int i, j;
+#ifdef INET6
+	uint32_t in6mtu;
 
-	/*
-	 * Try to update rt_mtu for all routes using this interface
-	 * Unfortunately the only way to do this is to traverse all
-	 * routing tables in all fibs/domains.
-	 */
-	for (i = 1; i <= AF_MAX; i++) {
-		mtu = if_getmtu_family(ifp, i);
-		for (j = 0; j < rt_numfibs; j++) {
-			rnh = rt_tables_get_rnh(j, i);
-			if (rnh == NULL)
-				continue;
-			nhops_update_ifmtu(rnh, ifp, mtu);
-		}
+	in6mtu = in6_ifmtu(ifp);
+#endif
+
+	for (u_int j = 0; j < rt_numfibs; j++) {
+#ifdef INET
+		rnh = rt_tables_get_rnh(j, AF_INET);
+		nhops_update_ifmtu(rnh, ifp, ifp->if_mtu);
+#endif
+#ifdef INET6
+		rnh = rt_tables_get_rnh(j, AF_INET6);
+		nhops_update_ifmtu(rnh, ifp, in6mtu);
+#endif
 	}
 }
 

sys/netinet6/in6.c

@@ -2612,12 +2612,9 @@ in6_domifattach(struct ifnet *ifp)
 	return ext;
 }
 
-int
-in6_domifmtu(struct ifnet *ifp)
+uint32_t
+in6_ifmtu(struct ifnet *ifp)
 {
-	if (ifp->if_afdata[AF_INET6] == NULL)
-		return ifp->if_mtu;
-
 	return (IN6_LINKMTU(ifp));
 }
 

sys/netinet6/in6_proto.c

@@ -113,7 +113,6 @@ struct domain inet6domain = {
 #endif
 	.dom_ifattach =		in6_domifattach,
 	.dom_ifdetach =		in6_domifdetach,
-	.dom_ifmtu    =		in6_domifmtu,
 	.dom_nprotosw =		14,
 	.dom_protosw = {
 		&tcp6_protosw,

sys/netinet6/in6_var.h

@@ -869,7 +869,7 @@ int	in6if_do_dad(struct ifnet *);
 void	in6_savemkludge(struct in6_ifaddr *);
 void	*in6_domifattach(struct ifnet *);
 void	in6_domifdetach(struct ifnet *, void *);
-int	in6_domifmtu(struct ifnet *);
+uint32_t in6_ifmtu(struct ifnet *);
 struct rib_head *in6_inithead(uint32_t fibnum);
 void	in6_detachhead(struct rib_head *rh);
 int	in6_if2idlen(struct ifnet *);

sys/sys/domain.h

@@ -58,8 +58,6 @@ struct domain {
 		(struct rib_head *);
 	void	*(*dom_ifattach)(struct ifnet *);
 	void	(*dom_ifdetach)(struct ifnet *, void *);
-	int	(*dom_ifmtu)(struct ifnet *);
-					/* af-dependent data on ifnet */
 	struct	protosw *dom_protosw[];
 };