Subject: Re: ipv6: Add support for RTA_PREFSRC

From: Daniel Walter <[email-masked]>
Date: Mon, 4 Apr 2011 09:56:44 +0200

On Fri, 2011-04-01 at 20:46 -0700, David Miller wrote:
> You can't change the layout of "struct in6_rtmsg", as that structure
> is explicitly exported to user space and changing it will break every
> application out there.

Hi,

I've kicked support for setting the preferred source via ioctl,
to keep "struct in6_rtmsg" untouched.
This reduces the RTA_PREFSRC support to netlink only, unless
we break the struct.

Do you see any other way around this problem?

regards,
daniel

---

diff --git a/include/net/ip6_fib.h b/include/net/ip6_fib.h
index bc3cde0..98348d5 100644
--- a/include/net/ip6_fib.h
+++ b/include/net/ip6_fib.h
@@ -42,6 +42,7 @@ struct fib6_config {
 
 	struct in6_addr	fc_dst;
 	struct in6_addr	fc_src;
+	struct in6_addr	fc_prefsrc;
 	struct in6_addr	fc_gateway;
 
 	unsigned long	fc_expires;
@@ -107,6 +108,7 @@ struct rt6_info {
 	struct rt6key			rt6i_dst ____cacheline_aligned_in_smp;
 	u32				rt6i_flags;
 	struct rt6key			rt6i_src;
+	struct rt6key			rt6i_prefsrc;
 	u32				rt6i_metric;
 	u32				rt6i_peer_genid;
 
diff --git a/include/net/ip6_route.h b/include/net/ip6_route.h
index c850e5f..2b37c20 100644
--- a/include/net/ip6_route.h
+++ b/include/net/ip6_route.h
@@ -141,6 +141,7 @@ struct rt6_rtnl_dump_arg {
 extern int rt6_dump_route(struct rt6_info *rt, void *p_arg);
 extern void rt6_ifdown(struct net *net, struct net_device *dev);
 extern void rt6_mtu_change(struct net_device *dev, unsigned mtu);
+extern void rt6_remove_prefsrc(struct inet6_ifaddr *ifp);

 /*
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 3daaf3c..26f9e14 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -825,6 +825,8 @@ static void ipv6_del_addr(struct inet6_ifaddr *ifp)
 		dst_release(&rt->dst);
 	}
 
+	/* clean up prefsrc entries */
+	rt6_remove_prefsrc(ifp);
 out:
 	in6_ifa_put(ifp);
 }
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 1820887..e2d8463 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -930,10 +930,14 @@ static int ip6_dst_lookup_tail(struct sock *sk,
 		goto out_err_release;
 
 	if (ipv6_addr_any(&fl6->saddr)) {
-		err = ipv6_dev_get_saddr(net, ip6_dst_idev(*dst)->dev,
-					 &fl6->daddr,
-					 sk ? inet6_sk(sk)->srcprefs : 0,
-					 &fl6->saddr);
+		struct rt6_info *rt = (struct rt6_info *) *dst;
+		if (rt->rt6i_prefsrc.plen)
+			ipv6_addr_copy(&fl6->saddr, &rt->rt6i_prefsrc.addr);
+		else
+			err = ipv6_dev_get_saddr(net, ip6_dst_idev(*dst)->dev,
+						 &fl6->daddr,
+						 sk ? inet6_sk(sk)->srcprefs : 0,
+						 &fl6->saddr);
 		if (err)
 			goto out_err_release;
 	}
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 843406f..f59dbae 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -1325,6 +1325,20 @@ int ip6_route_add(struct fib6_config *cfg)
 	if (dev == NULL)
 		goto out;
 
+	/* check if prefsrc is set */
+	if (!ipv6_addr_any(&cfg->fc_prefsrc)) {
+		struct in6_addr saddr_buf;
+		ipv6_addr_copy(&saddr_buf, &cfg->fc_prefsrc);
+		if (!ipv6_chk_addr(net, &saddr_buf, dev, 0)) {
+			printk(KERN_DEBUG "invalid pref_src\n");
+			err = -EINVAL;
+			goto out;
+		}
+		ipv6_addr_copy(&rt->rt6i_prefsrc.addr, &cfg->fc_prefsrc);
+		rt->rt6i_prefsrc.plen = 128;
+	} else
+		rt->rt6i_prefsrc.plen = 0;
+
 	if (cfg->fc_flags & (RTF_GATEWAY | RTF_NONEXTHOP)) {
 		rt->rt6i_nexthop = __neigh_lookup_errno(&nd_tbl, &rt->rt6i_gateway, dev);
 		if (IS_ERR(rt->rt6i_nexthop)) {
@@ -2037,6 +2051,39 @@ struct rt6_info *addrconf_dst_alloc(struct inet6_dev *idev,
 	return rt;
 }
 
+/* remove deleted ip from prefsrc entries */
+struct arg_dev_net_ip {
+	struct net_device *dev;
+	struct net *net;
+	struct in6_addr *addr;
+};
+
+static int fib6_remove_prefsrc(struct rt6_info *rt, void *arg)
+{
+	struct net_device *dev = ((struct arg_dev_net_ip *)arg)->dev;
+	struct net *net = ((struct arg_dev_net_ip *)arg)->net;
+	struct in6_addr *addr = ((struct arg_dev_net_ip *)arg)->addr;
+
+	if (((void *)rt->rt6i_dev == dev || dev == NULL) &&
+	    rt != net->ipv6.ip6_null_entry &&
+	    ipv6_addr_equal(addr, &rt->rt6i_prefsrc.addr)) {
+		/* remove prefsrc entry */
+		rt->rt6i_prefsrc.plen = 0;
+	}
+	return 0;
+}
+
+void rt6_remove_prefsrc(struct inet6_ifaddr *ifp)
+{
+	struct net *net = dev_net(ifp->idev->dev);
+	struct arg_dev_net_ip adni = {
+		.dev = ifp->idev->dev,
+		.net = net,
+		.addr = &ifp->addr,
+	};
+	fib6_clean_all(net, fib6_remove_prefsrc, 0, &adni);
+}
+
 struct arg_dev_net {
 	struct net_device *dev;
 	struct net *net;
@@ -2183,6 +2230,9 @@ static int rtm_to_fib6_config(struct sk_buff *skb, struct nlmsghdr *nlh,
 		nla_memcpy(&cfg->fc_src, tb[RTA_SRC], plen);
 	}
 
+	if (tb[RTA_PREFSRC])
+		nla_memcpy(&cfg->fc_prefsrc, tb[RTA_PREFSRC], 16);
+
 	if (tb[RTA_OIF])
 		cfg->fc_ifindex = nla_get_u32(tb[RTA_OIF]);
 
@@ -2325,11 +2375,22 @@ static int rt6_fill_node(struct net *net,
 #endif
 			NLA_PUT_U32(skb, RTA_IIF, iif);
 	} else if (dst) {
-		struct inet6_dev *idev = ip6_dst_idev(&rt->dst);
 		struct in6_addr saddr_buf;
-		if (ipv6_dev_get_saddr(net, idev ? idev->dev : NULL,
-				       dst, 0, &saddr_buf) == 0)
+		if (rt->rt6i_prefsrc.plen) {
+			ipv6_addr_copy(&saddr_buf, &rt->rt6i_prefsrc.addr);
 			NLA_PUT(skb, RTA_PREFSRC, 16, &saddr_buf);
+		} else {
+			struct inet6_dev *idev = ip6_dst_idev(&rt->dst);
+			if (ipv6_dev_get_saddr(net, idev ? idev->dev : NULL,
+					       dst, 0, &saddr_buf) == 0)
+				NLA_PUT(skb, RTA_PREFSRC, 16, &saddr_buf);
+		}
+	}
+
+	if (rt->rt6i_prefsrc.plen) {
+		struct in6_addr saddr_buf;
+		ipv6_addr_copy(&saddr_buf, &rt->rt6i_prefsrc.addr);
+		NLA_PUT(skb, RTA_PREFSRC, 16, &saddr_buf);
 	}
 
 	if (rtnetlink_put_metrics(skb, dst_metrics_ptr(&rt->dst)) < 0)

Daniel Walter
Software Engineer

Barracuda Networks AG
Eduard-Bodem-Gasse 1
6020 Innsbruck
Austria

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