Re: [PATCH net] net: ipv6: Fix ping to link-local addresses.

ping_v6_sendmsg never sets flowi6_oif, so it is not possible to
ping an IPv6 address on a different interface. Instead, it sets
flowi6_iif, which is incorrect but harmless. Also, it returns an
error if a passed-in scope ID doesn't match sk_bound_dev_if.

Get rid of the error, stop setting flowi6_iif, and support
various ways of setting oif in the same priority order used by
udpv6_sendmsg.

Tested: https://android-review.googlesource.com/#/c/254470/
Signed-off-by: Lorenzo Colitti <redacted>
---
 net/ipv6/ping.c | 29 +++++++++++++++--------------
 1 file changed, 15 insertions(+), 14 deletions(-)

diff --git a/net/ipv6/ping.c b/net/ipv6/ping.c
index fed40d1..eabf1ea 100644
--- a/net/ipv6/ping.c
+++ b/net/ipv6/ping.c

@@ -55,7 +55,7 @@ static 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;
 	struct dst_entry *dst;

@@ -78,23 +78,28 @@ static 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;
-		}