From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ed Swierk Subject: [PATCH] openvswitch: Trim off padding before L3 conntrack processing Date: Tue, 12 Dec 2017 08:17:19 -0800 Message-ID: <1513095439-128864-1-git-send-email-eswierk@skyportsystems.com> Cc: Lance Richardson , Ed Swierk , Benjamin Warren , Keith Holleman To: ovs-dev@openvswitch.org, netdev@vger.kernel.org, Pravin Shelar Return-path: Received: from mail-pg0-f68.google.com ([74.125.83.68]:38668 "EHLO mail-pg0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751641AbdLLQSD (ORCPT ); Tue, 12 Dec 2017 11:18:03 -0500 Received: by mail-pg0-f68.google.com with SMTP id f12so13728760pgo.5 for ; Tue, 12 Dec 2017 08:18:03 -0800 (PST) Sender: netdev-owner@vger.kernel.org List-ID: A short IPv4 packet may have up to 6 bytes of padding following the IP payload when received on an Ethernet device. In the normal IPv4 receive path, ip_rcv() trims the packet to ip_hdr->tot_len before invoking NF_INET_PRE_ROUTING hooks (including conntrack). Then any subsequent L3+ processing steps, like nf_checksum(), use skb->len as the length of the packet, rather than referring back to ip_hdr->tot_len. In the IPv6 receive path, ip6_rcv() does the same using ipv6_hdr->payload_len. In the OVS conntrack receive path, this trimming does not occur, so the checksum verification in tcp_header() fails, printing "nf_ct_tcp: bad TCP checksum". Extra zero bytes don't affect the checksum, but the length in the IP pseudoheader does. That length is based on skb->len, and without trimming, it doesn't match the length the sender used when computing the checksum. With this change, OVS conntrack trims IPv4 and IPv6 packets prior to L3 processing. Signed-off-by: Ed Swierk --- net/openvswitch/conntrack.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/net/openvswitch/conntrack.c b/net/openvswitch/conntrack.c index d558e882ca0c..3a7c9215c431 100644 --- a/net/openvswitch/conntrack.c +++ b/net/openvswitch/conntrack.c @@ -1105,12 +1105,29 @@ int ovs_ct_execute(struct net *net, struct sk_buff *skb, const struct ovs_conntrack_info *info) { int nh_ofs; + unsigned int nh_len; int err; /* The conntrack module expects to be working at L3. */ nh_ofs = skb_network_offset(skb); skb_pull_rcsum(skb, nh_ofs); + /* Trim to L3 length since nf_checksum() doesn't expect padding. */ + switch (skb->protocol) { + case htons(ETH_P_IP): + nh_len = ntohs(ip_hdr(skb)->tot_len); + break; + case htons(ETH_P_IPV6): + nh_len = ntohs(ipv6_hdr(skb)->payload_len) + + sizeof(struct ipv6hdr); + break; + default: + nh_len = skb->len; + } + err = pskb_trim_rcsum(skb, nh_len); + if (err) + return err; + if (key->ip.frag != OVS_FRAG_TYPE_NONE) { err = handle_fragments(net, key, info->zone.id, skb); if (err) -- 2.11.0