[PATCHv2 net] ipv6: use rt6_info members when dst is set in rt6_fill_node

[PATCHv2 net] ipv6: use rt6_info members when dst is set in rt6_fill_node

[Xin Long]

In inet6_rtm_getroute, since Commit 93531c674315 ("net/ipv6: separate
handling of FIB entries from dst based routes"), it has used rt->from
to dump route info instead of rt.

However for some route like cache, some of its information like flags
or gateway is not the same as that of the 'from' one. It caused 'ip
route get' to dump the wrong route information.

In Jianlin's testing, the output information even lost the expiration
time for a pmtu route cache due to the wrong fib6_flags.

So change to use rt6_info members for dst addr, src addr, flags and
gateway when it tries to dump a route entry without fibmatch set.

v1->v2:
  - not use rt6i_prefsrc.
  - also fix the gw dump issue.

Fixes: 93531c674315 ("net/ipv6: separate handling of FIB entries from dst based routes")
Reported-by: Jianlin Shi <jishi@redhat.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
---
 net/ipv6/route.c | 42 ++++++++++++++++++++++++++++++------------
 1 file changed, 30 insertions(+), 12 deletions(-)

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 18e00ce..3eed045 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -4670,20 +4670,31 @@ static int rt6_fill_node(struct net *net, struct sk_buff *skb,
 			 int iif, int type, u32 portid, u32 seq,
 			 unsigned int flags)
 {
-	struct rtmsg *rtm;
+	struct rt6_info *rt6 = (struct rt6_info *)dst;
+	struct rt6key *rt6_dst, *rt6_src;
+	u32 *pmetrics, table, rt6_flags;
 	struct nlmsghdr *nlh;
+	struct rtmsg *rtm;
 	long expires = 0;
-	u32 *pmetrics;
-	u32 table;
 
 	nlh = nlmsg_put(skb, portid, seq, type, sizeof(*rtm), flags);
 	if (!nlh)
 		return -EMSGSIZE;
 
+	if (rt6) {
+		rt6_dst = &rt6->rt6i_dst;
+		rt6_src = &rt6->rt6i_src;
+		rt6_flags = rt6->rt6i_flags;
+	} else {
+		rt6_dst = &rt->fib6_dst;
+		rt6_src = &rt->fib6_src;
+		rt6_flags = rt->fib6_flags;
+	}
+
 	rtm = nlmsg_data(nlh);
 	rtm->rtm_family = AF_INET6;
-	rtm->rtm_dst_len = rt->fib6_dst.plen;
-	rtm->rtm_src_len = rt->fib6_src.plen;
+	rtm->rtm_dst_len = rt6_dst->plen;
+	rtm->rtm_src_len = rt6_src->plen;
 	rtm->rtm_tos = 0;
 	if (rt->fib6_table)
 		table = rt->fib6_table->tb6_id;
@@ -4698,7 +4709,7 @@ static int rt6_fill_node(struct net *net, struct sk_buff *skb,
 	rtm->rtm_scope = RT_SCOPE_UNIVERSE;
 	rtm->rtm_protocol = rt->fib6_protocol;
 
-	if (rt->fib6_flags & RTF_CACHE)
+	if (rt6_flags & RTF_CACHE)
 		rtm->rtm_flags |= RTM_F_CLONED;
 
 	if (dest) {
@@ -4706,7 +4717,7 @@ static int rt6_fill_node(struct net *net, struct sk_buff *skb,
 			goto nla_put_failure;
 		rtm->rtm_dst_len = 128;
 	} else if (rtm->rtm_dst_len)
-		if (nla_put_in6_addr(skb, RTA_DST, &rt->fib6_dst.addr))
+		if (nla_put_in6_addr(skb, RTA_DST, &rt6_dst->addr))
 			goto nla_put_failure;
 #ifdef CONFIG_IPV6_SUBTREES
 	if (src) {
@@ -4714,12 +4725,12 @@ static int rt6_fill_node(struct net *net, struct sk_buff *skb,
 			goto nla_put_failure;
 		rtm->rtm_src_len = 128;
 	} else if (rtm->rtm_src_len &&
-		   nla_put_in6_addr(skb, RTA_SRC, &rt->fib6_src.addr))
+		   nla_put_in6_addr(skb, RTA_SRC, &rt6_src->addr))
 		goto nla_put_failure;
 #endif
 	if (iif) {
 #ifdef CONFIG_IPV6_MROUTE
-		if (ipv6_addr_is_multicast(&rt->fib6_dst.addr)) {
+		if (ipv6_addr_is_multicast(&rt6_dst->addr)) {
 			int err = ip6mr_get_route(net, skb, rtm, portid);
 
 			if (err == 0)
@@ -4754,7 +4765,14 @@ static int rt6_fill_node(struct net *net, struct sk_buff *skb,
 	/* For multipath routes, walk the siblings list and add
 	 * each as a nexthop within RTA_MULTIPATH.
 	 */
-	if (rt->fib6_nsiblings) {
+	if (rt6) {
+		if (rt6_flags & RTF_GATEWAY &&
+		    nla_put_in6_addr(skb, RTA_GATEWAY, &rt6->rt6i_gateway))
+			goto nla_put_failure;
+
+		if (dst->dev && nla_put_u32(skb, RTA_OIF, dst->dev->ifindex))
+			goto nla_put_failure;
+	} else if (rt->fib6_nsiblings) {
 		struct fib6_info *sibling, *next_sibling;
 		struct nlattr *mp;
 
@@ -4777,7 +4795,7 @@ static int rt6_fill_node(struct net *net, struct sk_buff *skb,
 			goto nla_put_failure;
 	}
 
-	if (rt->fib6_flags & RTF_EXPIRES) {
+	if (rt6_flags & RTF_EXPIRES) {
 		expires = dst ? dst->expires : rt->expires;
 		expires -= jiffies;
 	}
@@ -4785,7 +4803,7 @@ static int rt6_fill_node(struct net *net, struct sk_buff *skb,
 	if (rtnl_put_cacheinfo(skb, dst, 0, expires, dst ? dst->error : 0) < 0)
 		goto nla_put_failure;
 
-	if (nla_put_u8(skb, RTA_PREF, IPV6_EXTRACT_PREF(rt->fib6_flags)))
+	if (nla_put_u8(skb, RTA_PREF, IPV6_EXTRACT_PREF(rt6_flags)))
 		goto nla_put_failure;
 
 
-- 
2.1.0

Re: [PATCHv2 net] ipv6: use rt6_info members when dst is set in rt6_fill_node

[David Miller]

From: Xin Long <lucien.xin@gmail.com>
Date: Tue, 11 Sep 2018 14:33:58 +0800

> In inet6_rtm_getroute, since Commit 93531c674315 ("net/ipv6: separate
> handling of FIB entries from dst based routes"), it has used rt->from
> to dump route info instead of rt.
> 
> However for some route like cache, some of its information like flags
> or gateway is not the same as that of the 'from' one. It caused 'ip
> route get' to dump the wrong route information.
> 
> In Jianlin's testing, the output information even lost the expiration
> time for a pmtu route cache due to the wrong fib6_flags.
> 
> So change to use rt6_info members for dst addr, src addr, flags and
> gateway when it tries to dump a route entry without fibmatch set.
> 
> v1->v2:
>   - not use rt6i_prefsrc.
>   - also fix the gw dump issue.
> 
> Fixes: 93531c674315 ("net/ipv6: separate handling of FIB entries from dst based routes")
> Reported-by: Jianlin Shi <jishi@redhat.com>
> Signed-off-by: Xin Long <lucien.xin@gmail.com>

Applied and queued up for -stable, thanks Xin.