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

@@ -106,16 +111,12 @@ static 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.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;
-
 	ipc6.tclass = np->tclass;
 	fl6.flowlabel = ip6_make_flowinfo(ipc6.tclass, fl6.flowlabel);