Revert "sock: Reset dst when changing sk_mark via setsockopt"

BugLink: https://bugs.launchpad.net/bugs/1854857

This reverts commit 4c5ce7ca90e00164f954d727215fc227addc467c which is
commit 50254256 upstream.

It breaks a number of runtime Android networking tests, so something is
wrong with the backport, or something else also needed to be backported
at the same time.  So I'm dropping this from the tree as regressions are
not good.

Cc: David Barmann <david.barmann@stackpath.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Connor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

net/core/sock.c

@@ -952,12 +952,10 @@ int sock_setsockopt(struct socket *sock, int level, int optname,
 			clear_bit(SOCK_PASSSEC, &sock->flags);
 		break;
 	case SO_MARK:
-		if (!ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN)) {
+		if (!ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN))
 			ret = -EPERM;
-		} else if (val != sk->sk_mark) {
+		else
 			sk->sk_mark = val;
-			sk_dst_reset(sk);
-		}
 		break;
 
 	case SO_RXQ_OVFL: