Change the way we automatically add prefix routes when adding a new address.

This makes it possible to have more than one address with the same prefix.
The first address added is used for the route. On deletion of an address
with IFA_ROUTE set, we try to find a "fallback" address and hand over the
route if possible.
I plan to MFC this in 4 weeks, hence I keep the - now obsolete - argument to
in_ifscrub as it must be considered KAPI as it is not static in in.c. I will
clean this after the MFC.

Discussed on:	arch, net
Tested by:	many testers of the CARP patches
Nits from:	ru, Andrea Campi <andrea+freebsd_arch webcom it>
Obtained from:	WIDE via OpenBSD
MFC after:	1 month

1 files changed, 147 insertions, 27 deletions

diff --git a/sys/netinet/in.c b/sys/netinet/in.c
index 43a5260..3d520b4 100644
--- a/sys/netinet/in.c
+++ b/sys/netinet/in.c
@@ -1,4 +1,32 @@
 /*
+ * Copyright (C) 2001 WIDE Project.  All rights reserved.
+ * 
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the project nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+/*
  * Copyright (c) 1982, 1986, 1991, 1993
  *	The Regents of the University of California.  All rights reserved.
  *
@@ -55,6 +83,8 @@ static void in_len2mask(struct in_addr *, int);
 static int in_lifaddr_ioctl(struct socket *, u_long, caddr_t,
 	struct ifnet *, struct thread *);
 
+static int	in_addprefix(struct in_ifaddr *, int);
+static int	in_scrubprefix(struct in_ifaddr *);
 static void	in_socktrim(struct sockaddr_in *);
 static int	in_ifinit(struct ifnet *,
 	    struct in_ifaddr *, struct sockaddr_in *, int);
@@ -654,14 +684,7 @@ in_ifscrub(ifp, ia)
 	register struct ifnet *ifp;
 	register struct in_ifaddr *ia;
 {
-
-	if ((ia->ia_flags & IFA_ROUTE) == 0)
-		return;
-	if (ifp->if_flags & (IFF_LOOPBACK|IFF_POINTOPOINT))
-		rtinit(&(ia->ia_ifa), (int)RTM_DELETE, RTF_HOST);
-	else
-		rtinit(&(ia->ia_ifa), (int)RTM_DELETE, 0);
-	ia->ia_flags &= ~IFA_ROUTE;
+	in_scrubprefix(ia);
 }
 
 /*
@@ -743,25 +766,8 @@ in_ifinit(ifp, ia, sin, scrub)
 			return (0);
 		flags |= RTF_HOST;
 	}
-
-	/*-
-	 * Don't add host routes for interface addresses of
-	 * 0.0.0.0 --> 0.255.255.255 netmask 255.0.0.0.  This makes it
-	 * possible to assign several such address pairs with consistent
-	 * results (no host route) and is required by BOOTP.
-	 *
-	 * XXX: This is ugly !  There should be a way for the caller to
-	 *      say that they don't want a host route.
-	 */
-	if (ia->ia_addr.sin_addr.s_addr != INADDR_ANY ||
-	    ia->ia_netmask != IN_CLASSA_NET ||
-	    ia->ia_dstaddr.sin_addr.s_addr != htonl(IN_CLASSA_HOST)) {
-		if ((error = rtinit(&ia->ia_ifa, (int)RTM_ADD, flags)) != 0) {
-			ia->ia_addr = oldaddr;
-			return (error);
-		}
-		ia->ia_flags |= IFA_ROUTE;
-	}
+	if ((error = in_addprefix(ia, flags)) != 0)
+		return (error);
 
 	/*
 	 * If the interface supports multicast, join the "all hosts"
@@ -776,6 +782,120 @@ in_ifinit(ifp, ia, sin, scrub)
 	return (error);
 }
 
+#define rtinitflags(x) \
+	((((x)->ia_ifp->if_flags & (IFF_LOOPBACK | IFF_POINTOPOINT)) != 0) \
+	    ? RTF_HOST : 0)
+/*
+ * Check if we have a route for the given prefix already or add a one
+ * accordingly.
+ */
+static int
+in_addprefix(target, flags)
+	struct in_ifaddr *target;
+	int flags;
+{
+	struct in_ifaddr *ia;
+	struct in_addr prefix, mask, p;
+	int error;
+
+	if ((flags & RTF_HOST) != 0)
+		prefix = target->ia_dstaddr.sin_addr;
+	else {
+		prefix = target->ia_addr.sin_addr;
+		mask = target->ia_sockmask.sin_addr;
+		prefix.s_addr &= mask.s_addr;
+	}
+
+	TAILQ_FOREACH(ia, &in_ifaddrhead, ia_link) {
+		if (rtinitflags(ia))
+			p = ia->ia_dstaddr.sin_addr;
+		else {
+			p = ia->ia_addr.sin_addr;
+			p.s_addr &= ia->ia_sockmask.sin_addr.s_addr;
+		}
+
+		if (prefix.s_addr != p.s_addr)
+			continue;
+
+		/*
+		 * If we got a matching prefix route inserted by other
+		 * interface address, we are done here.
+		 */
+		if (ia->ia_flags & IFA_ROUTE)
+			return 0;
+	}
+
+	/*
+	 * No-one seem to have this prefix route, so we try to insert it.
+	 */
+	error = rtinit(&target->ia_ifa, (int)RTM_ADD, flags);
+	if (!error)
+		target->ia_flags |= IFA_ROUTE;
+	return error;
+}
+
+/*
+ * If there is no other address in the system that can serve a route to the
+ * same prefix, remove the route.  Hand over the route to the new address
+ * otherwise.
+ */
+static int
+in_scrubprefix(target)
+	struct in_ifaddr *target;
+{
+	struct in_ifaddr *ia;
+	struct in_addr prefix, mask, p;
+	int error;
+
+	if ((target->ia_flags & IFA_ROUTE) == 0)
+		return 0;
+
+	if (rtinitflags(target))
+		prefix = target->ia_dstaddr.sin_addr;
+	else {
+		prefix = target->ia_addr.sin_addr;
+		mask = target->ia_sockmask.sin_addr;
+		prefix.s_addr &= mask.s_addr;
+	}
+
+	TAILQ_FOREACH(ia, &in_ifaddrhead, ia_link) {
+		if (rtinitflags(ia))
+			p = ia->ia_dstaddr.sin_addr;
+		else {
+			p = ia->ia_addr.sin_addr;
+			p.s_addr &= ia->ia_sockmask.sin_addr.s_addr;
+		}
+
+		if (prefix.s_addr != p.s_addr)
+			continue;
+
+		/*
+		 * If we got a matching prefix address, move IFA_ROUTE and
+		 * the route itself to it.  Make sure that routing daemons
+		 * get a heads-up.
+		 */
+		if ((ia->ia_flags & IFA_ROUTE) == 0) {
+			rtinit(&(target->ia_ifa), (int)RTM_DELETE,
+			    rtinitflags(target));
+			target->ia_flags &= ~IFA_ROUTE;
+
+			error = rtinit(&ia->ia_ifa, (int)RTM_ADD,
+			    rtinitflags(ia) | RTF_UP);
+			if (error == 0)
+				ia->ia_flags |= IFA_ROUTE;
+			return error;
+		}
+	}
+
+	/*
+	 * As no-one seem to have this prefix, we can remove the route.
+	 */
+	rtinit(&(target->ia_ifa), (int)RTM_DELETE, rtinitflags(target));
+	target->ia_flags &= ~IFA_ROUTE;
+	return 0;
+}
+
+#undef rtinitflags
 
 /*
  * Return 1 if the address might be a local broadcast address.