| Message ID | 20120217101648.01f31fcd@nehalam.linuxnetplumber.net |
|---|---|
| State | Not Applicable, archived |
| Delegated to: | David Miller |
| Headers | show |
Hi Stephen, On Fri, Feb 17, 2012 at 10:16:48AM -0800, Stephen Hemminger wrote: > If UDP packet with extra padding is received on a device that > does hardware checksumming (but not checking) is processed > by netfilter conntrack, it would generate a bogus warning > about the checksum being incorrect. > > There were two possible solutions. The netfilter conntrack > code could trim the packet, discarding the extra padding > and adjusting the checksum. Or it can force regular > non-offloaded checksum. This patch implements the latter > on the principal that is better for firewall code to not > modify the packet. I like this approach. > Compile tested only; haven't been able to reproduce the > problem yet. Let me know if I should pass this to davem once you confirm this fixes the problem you're noticing. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
--- a/net/netfilter/nf_conntrack_proto_udp.c 2012-01-10 10:57:00.407196614 -0800 +++ b/net/netfilter/nf_conntrack_proto_udp.c 2012-02-17 10:06:18.038472559 -0800 @@ -125,12 +125,17 @@ static int udp_error(struct net *net, st * We skip checking packets on the outgoing path * because the checksum is assumed to be correct. * FIXME: Source route IP option packets --RR */ - if (net->ct.sysctl_checksum && hooknum == NF_INET_PRE_ROUTING && - nf_checksum(skb, hooknum, dataoff, IPPROTO_UDP, pf)) { - if (LOG_INVALID(net, IPPROTO_UDP)) - nf_log_packet(pf, 0, skb, NULL, NULL, NULL, - "nf_ct_udp: bad UDP checksum "); - return -NF_ACCEPT; + if (net->ct.sysctl_checksum && hooknum == NF_INET_PRE_ROUTING) { + /* Special case for hardware checksum offload with padding */ + if (skb->ip_summed == CHECKSUM_COMPLETE && udplen > ntohs(hdr->len)) + skb->ip_summed = CHECKSUM_NONE; + + if (nf_checksum(skb, hooknum, dataoff, IPPROTO_UDP, pf)) { + if (LOG_INVALID(net, IPPROTO_UDP)) + nf_log_packet(pf, 0, skb, NULL, NULL, NULL, + "nf_ct_udp: bad UDP checksum "); + return -NF_ACCEPT; + } } return NF_ACCEPT;
If UDP packet with extra padding is received on a device that does hardware checksumming (but not checking) is processed by netfilter conntrack, it would generate a bogus warning about the checksum being incorrect. There were two possible solutions. The netfilter conntrack code could trim the packet, discarding the extra padding and adjusting the checksum. Or it can force regular non-offloaded checksum. This patch implements the latter on the principal that is better for firewall code to not modify the packet. Compile tested only; haven't been able to reproduce the problem yet. Signed-off-by: Stephen Hemminger <shemminger@vyatta.com> --- Patch against -net tree, after review/test it should go to stable as well. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html