netdev - Re: [patch net] udp6: respect IPV6_DONTFRAG sockopt in case there are pending frames

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Date:	Mon, 30 Sep 2013 23:21:55 +0200
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	Jiri Pirko <jiri@...nulli.us>, netdev@...r.kernel.org,
	davem@...emloft.net, kuznet@....inr.ac.ru, jmorris@...ei.org,
	kaber@...sh.net, yoshfuji@...ux-ipv6.org
Subject: Re: [patch net] udp6: respect IPV6_DONTFRAG sockopt in case there are pending frames

On Mon, Sep 30, 2013 at 07:56:40PM +0200, Hannes Frederic Sowa wrote:
> Hmm, I wonder if we need the same change in ipv6/raw.c.

Nope, ipv6/raw.c is fine.

> Looks good at first sight, but I need to do some more tests.

Strange, loopback traffic is not bound by the frag_size. This fixes it but
should not be necessary. Don't know the reason, yet.

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index a54c45c..9dd136e 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -124,7 +124,14 @@ static int ip6_finish_output2(struct sk_buff *skb)
 
 static int ip6_finish_output(struct sk_buff *skb)
 {
-	if ((skb->len > ip6_skb_dst_mtu(skb) && !skb_is_gso(skb)) ||
+	int mtu;
+	struct ipv6_pinfo *np = skb->sk ? inet6_sk(skb->sk) : NULL;
+
+	mtu = ip6_skb_dst_mtu(skb);
+	if (np && np->frag_size && np->frag_size < mtu)
+		mtu = np->frag_size;
+
+	if ((skb->len > mtu && !skb_is_gso(skb)) ||
 	    dst_allfrag(skb_dst(skb)))
 		return ip6_fragment(skb, ip6_finish_output2);
 	else


Regarding your patch, this is fine by me:

Acked-by: Hannes Frederic Sowa <hannes@...essinduktion.org>

Thanks,

  Hannes

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