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  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [thread-next>] [day] [month] [year] [list]
Date:   Sat, 23 Nov 2019 15:58:18 +0100
From:   Oliver Herms <>
Subject: [PATCH] net: ip/tnl: Set iph->id only when don't fragment is not set

In IPv4 the identification field ensures that fragments of different datagrams
are not mixed by the receiver. Packets with Don't Fragment (DF) flag set are not
to be fragmented in transit and thus don't need an identification.
Calculating the identification takes significant CPU time.
This patch will increase IP tunneling performance by ~10% unless DF is not set.
However, DF is set by default which is best practice.

Signed-off-by: Oliver Herms <>
 net/ipv4/ip_tunnel_core.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/ip_tunnel_core.c b/net/ipv4/ip_tunnel_core.c
index 1452a97914a0..8636c1e0e7b7 100644
--- a/net/ipv4/ip_tunnel_core.c
+++ b/net/ipv4/ip_tunnel_core.c
@@ -73,7 +73,9 @@ void iptunnel_xmit(struct sock *sk, struct rtable *rt, struct sk_buff *skb,
 	iph->daddr	=	dst;
 	iph->saddr	=	src;
 	iph->ttl	=	ttl;
-	__ip_select_ident(net, iph, skb_shinfo(skb)->gso_segs ?: 1);
+	if (unlikely((iph->frag_off & htons(IP_DF)) == false))
+		__ip_select_ident(net, iph, skb_shinfo(skb)->gso_segs ?: 1);
 	err = ip_local_out(net, sk, skb);

Powered by blists - more mailing lists