linux-kernel - [PATCH 5.7 005/244] ipv6: Fix use of anycast address with loopback

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Message-Id: <20200720152826.126487550@linuxfoundation.org>
Date:   Mon, 20 Jul 2020 17:34:36 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, thomas.gambier@...edi.com,
        David Ahern <dsahern@...nel.org>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 5.7 005/244] ipv6: Fix use of anycast address with loopback

From: David Ahern <dsahern@...nel.org>

[ Upstream commit aea23c323d89836bcdcee67e49def997ffca043b ]

Thomas reported a regression with IPv6 and anycast using the following
reproducer:

    echo 1 >  /proc/sys/net/ipv6/conf/all/forwarding
    ip -6 a add fc12::1/16 dev lo
    sleep 2
    echo "pinging lo"
    ping6 -c 2 fc12::

The conversion of addrconf_f6i_alloc to use ip6_route_info_create missed
the use of fib6_is_reject which checks addresses added to the loopback
interface and sets the REJECT flag as needed. Update fib6_is_reject for
loopback checks to handle RTF_ANYCAST addresses.

Fixes: c7a1ce397ada ("ipv6: Change addrconf_f6i_alloc to use ip6_route_info_create")
Reported-by: thomas.gambier@...edi.com
Signed-off-by: David Ahern <dsahern@...nel.org>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/ipv6/route.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -3402,7 +3402,7 @@ static bool fib6_is_reject(u32 flags, st
 	if ((flags & RTF_REJECT) ||
 	    (dev && (dev->flags & IFF_LOOPBACK) &&
 	     !(addr_type & IPV6_ADDR_LOOPBACK) &&
-	     !(flags & RTF_LOCAL)))
+	     !(flags & (RTF_ANYCAST | RTF_LOCAL))))
 		return true;
 
 	return false;