linux-kernel - [PATCH v3 net-next 1/3] ipv6: remove dst

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Message-ID: <e721c615e22fc4d3d53bfa230d5d71462ae9c9a8.1697779681.git.yan@cloudflare.com>
Date:   Thu, 19 Oct 2023 22:32:47 -0700
From:   Yan Zhai <yan@...udflare.com>
To:     netdev@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        David Ahern <dsahern@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, Aya Levin <ayal@...dia.com>,
        Tariq Toukan <tariqt@...dia.com>, linux-kernel@...r.kernel.org,
        kernel-team@...udflare.com, Florian Westphal <fw@...len.de>,
        Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        Alexander H Duyck <alexander.duyck@...il.com>
Subject: [PATCH v3 net-next 1/3] ipv6: remove dst_allfrag test on ipv6 output

dst_allfrag was added before the first git commit:

https://www.mail-archive.com/bk-commits-head@vger.kernel.org/msg03399.html

The feature would send packets to the fragmentation path if a box
receives a PMTU value with less than 1280 byte. However, since commit
9d289715eb5c ("ipv6: stop sending PTB packets for MTU < 1280"), such
message would be simply discarded. The feature flag is neither supported
in iproute2 utility. In theory one can still manipulate it with direct
netlink message, but it is not ideal because it was based on obsoleted
guidance of RFC-2460 (replaced by RFC-8200).

The feature test would always return false at the moment, so remove it
from the output path.

Signed-off-by: Yan Zhai <yan@...udflare.com>
---
 net/ipv6/ip6_output.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index a471c7e91761..ae87a3817d4a 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -189,7 +189,6 @@ static int __ip6_finish_output(struct net *net, struct sock *sk, struct sk_buff
 		return ip6_finish_output_gso_slowpath_drop(net, sk, skb, mtu);
 
 	if ((skb->len > mtu && !skb_is_gso(skb)) ||
-	    dst_allfrag(skb_dst(skb)) ||
 	    (IP6CB(skb)->frag_max_size && skb->len > IP6CB(skb)->frag_max_size))
 		return ip6_fragment(net, sk, skb, ip6_finish_output2);
 	else
-- 
2.30.2