netdev - Re: vxlan/veth performance issues on net.git + latest kernels

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Sun, 08 Dec 2013 12:50:24 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Mike Rapoport <mike.rapoport@...ellosystems.com>
Cc:	Or Gerlitz <ogerlitz@...lanox.com>,
	Or Gerlitz <or.gerlitz@...il.com>,
	Joseph Gasparakis <joseph.gasparakis@...el.com>,
	Pravin B Shelar <pshelar@...ira.com>,
	Jerry Chu <hkchu@...gle.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Alexei Starovoitov <ast@...mgrid.com>,
	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	"Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>,
	John Fastabend <john.fastabend@...il.com>
Subject: Re: vxlan/veth performance issues on net.git + latest kernels

On Sun, 2013-12-08 at 16:30 +0200, Mike Rapoport wrote:
>  
> It was something *very* hacky:

> 		if (skb->len < 64000)
> 			skb_shinfo(skb)->gso_size = skb->len;
> 		else
> 			skb_shinfo(skb)->gso_size = 64000;

This sounds like an 16bit overflow somewhere.

This reminds the issue we fix in commit 50bceae9bd356
("tcp: Reallocate headroom if it would overflow csum_start")

You might try to reduce the 0xFFFF to something smaller.

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 993da005e087..8364bcfe1e08 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2373,7 +2373,7 @@ int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
 	 * beyond what csum_start can cover.
 	 */
 	if (unlikely((NET_IP_ALIGN && ((unsigned long)skb->data & 3)) ||
-		     skb_headroom(skb) >= 0xFFFF)) {
+		     skb_headroom(skb) >= 0xFF00)) {
 		struct sk_buff *nskb = __pskb_copy(skb, MAX_TCP_HEADER,
 						   GFP_ATOMIC);
 		return nskb ? tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC) :


--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html