@@ -2804,7 +2804,6 @@ struct sk_buff *skb_segment(struct sk_buff *skb, netdev_features_t features)
tail = nskb;
__copy_skb_header(nskb, skb);
- nskb->mac_len = skb->mac_len;
/* nskb and skb might have different headroom */
if (nskb->ip_summed == CHECKSUM_PARTIAL)
@@ -2814,6 +2813,7 @@ struct sk_buff *skb_segment(struct sk_buff *skb, netdev_features_t features)
skb_set_network_header(nskb, skb->mac_len);
nskb->transport_header = (nskb->network_header +
skb_network_header_len(skb));
+ skb_reset_mac_len(nskb);
skb_copy_from_linear_data_offset(skb, -tnl_hlen,
nskb->data - tnl_hlen,
This is a note to let you know that I have just added a patch titled net: Correctly set segment mac_len in skb_segment(). to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree which can be found at: http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.11.y.z tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Luis ------ From aa405ecf83f5dd5e85eb640f70ca3c162594d799 Mon Sep 17 00:00:00 2001 From: Vlad Yasevich <vyasevic@redhat.com> Date: Thu, 31 Jul 2014 10:33:06 -0400 Subject: net: Correctly set segment mac_len in skb_segment(). commit fcdfe3a7fa4cb74391d42b6a26dc07c20dab1d82 upstream. When performing segmentation, the mac_len value is copied right out of the original skb. However, this value is not always set correctly (like when the packet is VLAN-tagged) and we'll end up copying a bad value. One way to demonstrate this is to configure a VM which tags packets internally and turn off VLAN acceleration on the forwarding bridge port. The packets show up corrupt like this: 16:18:24.985548 52:54:00:ab:be:25 > 52:54:00:26:ce:a3, ethertype 802.1Q (0x8100), length 1518: vlan 100, p 0, ethertype 0x05e0, 0x0000: 8cdb 1c7c 8cdb 0064 4006 b59d 0a00 6402 ...|...d@.....d. 0x0010: 0a00 6401 9e0d b441 0a5e 64ec 0330 14fa ..d....A.^d..0.. 0x0020: 29e3 01c9 f871 0000 0101 080a 000a e833)....q.........3 0x0030: 000f 8c75 6e65 7470 6572 6600 6e65 7470 ...unetperf.netp 0x0040: 6572 6600 6e65 7470 6572 6600 6e65 7470 erf.netperf.netp 0x0050: 6572 6600 6e65 7470 6572 6600 6e65 7470 erf.netperf.netp 0x0060: 6572 6600 6e65 7470 6572 6600 6e65 7470 erf.netperf.netp ... This also leads to awful throughput as GSO packets are dropped and cause retransmissions. The solution is to set the mac_len using the values already available in then new skb. We've already adjusted all of the header offset, so we might as well correctly figure out the mac_len using skb_reset_mac_len(). After this change, packets are segmented correctly and performance is restored. CC: Eric Dumazet <edumazet@google.com> Signed-off-by: Vlad Yasevich <vyasevic@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net> [ luis: backported to 3.11: used davem's backport to 3.10 ] Signed-off-by: Luis Henriques <luis.henriques@canonical.com> --- net/core/skbuff.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) -- 1.9.1