net: ipv6: Fix ping to link-local addresses.

ping_v6_sendmsg does not set flowi6_oif in response to
sin6_scope_id or sk_bound_dev_if, so it is not possible to use
these APIs to ping an IPv6 address on a different interface.
Instead, it sets flowi6_iif, which is incorrect but harmless.

Stop setting flowi6_iif, and support various ways of setting oif
in the same priority order used by udpv6_sendmsg.

[Backport of net 5e457896986e16c440c97bb94b9ccd95dd157292]

Bug: 29370996
Change-Id: Ibe1b9434c00ed96f1e30acb110734c6570b087b8
Tested: https://android-review.googlesource.com/#/c/254470/
Signed-off-by: Lorenzo Colitti <lorenzo@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 17 insertions, 21 deletions

diff --git a/net/ipv6/ping.c b/net/ipv6/ping.c
index 2cfaedf03252..9411c8d770a5 100644
--- a/net/ipv6/ping.c
+++ b/net/ipv6/ping.c
@@ -84,7 +84,7 @@ int ping_v6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 	struct icmp6hdr user_icmph;
 	int addr_type;
 	struct in6_addr *daddr;
-	int iif = 0;
+	int oif = 0;
 	struct flowi6 fl6;
 	int err;
 	int hlimit;
@@ -106,25 +106,30 @@ int ping_v6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 		if (u->sin6_family != AF_INET6) {
 			return -EAFNOSUPPORT;
 		}
-		if (sk->sk_bound_dev_if &&
-		    sk->sk_bound_dev_if != u->sin6_scope_id) {
-			return -EINVAL;
-		}
 		daddr = &(u->sin6_addr);
-		iif = u->sin6_scope_id;
+		if (__ipv6_addr_needs_scope_id(ipv6_addr_type(daddr)))
+			oif = u->sin6_scope_id;
 	} else {
 		if (sk->sk_state != TCP_ESTABLISHED)
 			return -EDESTADDRREQ;
 		daddr = &sk->sk_v6_daddr;
 	}
 
-	if (!iif)
-		iif = sk->sk_bound_dev_if;
+	if (!oif)
+		oif = sk->sk_bound_dev_if;
+
+	if (!oif)
+		oif = np->sticky_pktinfo.ipi6_ifindex;
+
+	if (!oif && ipv6_addr_is_multicast(daddr))
+		oif = np->mcast_oif;
+	else if (!oif)
+		oif = np->ucast_oif;
 
 	addr_type = ipv6_addr_type(daddr);
-	if (__ipv6_addr_needs_scope_id(addr_type) && !iif)
-		return -EINVAL;
-	if (addr_type & IPV6_ADDR_MAPPED)
+	if ((__ipv6_addr_needs_scope_id(addr_type) && !oif) ||
+	    (addr_type & IPV6_ADDR_MAPPED) ||
+	    (oif && sk->sk_bound_dev_if && oif != sk->sk_bound_dev_if))
 		return -EINVAL;
 
 	/* TODO: use ip6_datagram_send_ctl to get options from cmsg */
@@ -134,17 +139,13 @@ int ping_v6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 	fl6.flowi6_proto = IPPROTO_ICMPV6;
 	fl6.saddr = np->saddr;
 	fl6.daddr = *daddr;
+	fl6.flowi6_oif = oif;
 	fl6.flowi6_mark = sk->sk_mark;
 	fl6.flowi6_uid = sock_i_uid(sk);
 	fl6.fl6_icmp_type = user_icmph.icmp6_type;
 	fl6.fl6_icmp_code = user_icmph.icmp6_code;
 	security_sk_classify_flow(sk, flowi6_to_flowi(&fl6));
 
-	if (!fl6.flowi6_oif && ipv6_addr_is_multicast(&fl6.daddr))
-		fl6.flowi6_oif = np->mcast_oif;
-	else if (!fl6.flowi6_oif)
-		fl6.flowi6_oif = np->ucast_oif;
-
 	dst = ip6_sk_dst_lookup_flow(sk, &fl6,  daddr);
 	if (IS_ERR(dst))
 		return PTR_ERR(dst);
@@ -154,11 +155,6 @@ int ping_v6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 	if (!np)
 		return -EBADF;
 
-	if (!fl6.flowi6_oif && ipv6_addr_is_multicast(&fl6.daddr))
-		fl6.flowi6_oif = np->mcast_oif;
-	else if (!fl6.flowi6_oif)
-		fl6.flowi6_oif = np->ucast_oif;
-
 	pfh.icmph.type = user_icmph.icmp6_type;
 	pfh.icmph.code = user_icmph.icmp6_code;
 	pfh.icmph.checksum = 0;