target/linux/brcm2708/patches-4.4/0221-bpf-add-skb_postpush_rcsum-and-fix-dev_forward_skb-o.patch

   1 From 367956e87b62ae1f015ccbff58c7920a2e7a3511 Mon Sep 17 00:00:00 2001
   2 From: Daniel Borkmann <daniel@iogearbox.net>
   3 Date: Thu, 7 Jan 2016 15:50:23 +0100
   4 Subject: [PATCH 221/423] bpf: add skb_postpush_rcsum and fix dev_forward_skb
   5  occasions
   6
   7 Add a small helper skb_postpush_rcsum() and fix up redirect locations
   8 that need CHECKSUM_COMPLETE fixups on ingress. dev_forward_skb() expects
   9 a proper csum that covers also Ethernet header, f.e. since 2c26d34bbcc0
  10 ("net/core: Handle csum for CHECKSUM_COMPLETE VXLAN forwarding"), we
  11 also do skb_postpull_rcsum() after pulling Ethernet header off via
  12 eth_type_trans().
  13
  14 When using eBPF in a netns setup f.e. with vxlan in collect metadata mode,
  15 I can trigger the following csum issue with an IPv6 setup:
  16
  17   [  505.144065] dummy1: hw csum failure
  18   [...]
  19   [  505.144108] Call Trace:
  20   [  505.144112]  <IRQ>  [<ffffffff81372f08>] dump_stack+0x44/0x5c
  21   [  505.144134]  [<ffffffff81607cea>] netdev_rx_csum_fault+0x3a/0x40
  22   [  505.144142]  [<ffffffff815fee3f>] __skb_checksum_complete+0xcf/0xe0
  23   [  505.144149]  [<ffffffff816f0902>] nf_ip6_checksum+0xb2/0x120
  24   [  505.144161]  [<ffffffffa08c0e0e>] icmpv6_error+0x17e/0x328 [nf_conntrack_ipv6]
  25   [  505.144170]  [<ffffffffa0898eca>] ? ip6t_do_table+0x2fa/0x645 [ip6_tables]
  26   [  505.144177]  [<ffffffffa08c0725>] ? ipv6_get_l4proto+0x65/0xd0 [nf_conntrack_ipv6]
  27   [  505.144189]  [<ffffffffa06c9a12>] nf_conntrack_in+0xc2/0x5a0 [nf_conntrack]
  28   [  505.144196]  [<ffffffffa08c039c>] ipv6_conntrack_in+0x1c/0x20 [nf_conntrack_ipv6]
  29   [  505.144204]  [<ffffffff8164385d>] nf_iterate+0x5d/0x70
  30   [  505.144210]  [<ffffffff816438d6>] nf_hook_slow+0x66/0xc0
  31   [  505.144218]  [<ffffffff816bd302>] ipv6_rcv+0x3f2/0x4f0
  32   [  505.144225]  [<ffffffff816bca40>] ? ip6_make_skb+0x1b0/0x1b0
  33   [  505.144232]  [<ffffffff8160b77b>] __netif_receive_skb_core+0x36b/0x9a0
  34   [  505.144239]  [<ffffffff8160bdc8>] ? __netif_receive_skb+0x18/0x60
  35   [  505.144245]  [<ffffffff8160bdc8>] __netif_receive_skb+0x18/0x60
  36   [  505.144252]  [<ffffffff8160ccff>] process_backlog+0x9f/0x140
  37   [  505.144259]  [<ffffffff8160c4a5>] net_rx_action+0x145/0x320
  38   [...]
  39
  40 What happens is that on ingress, we push Ethernet header back in, either
  41 from cls_bpf or right before skb_do_redirect(), but without updating csum.
  42 The "hw csum failure" can be fixed by using the new skb_postpush_rcsum()
  43 helper for the dev_forward_skb() case to correct the csum diff again.
  44
  45 Thanks to Hannes Frederic Sowa for the csum_partial() idea!
  46
  47 Fixes: 3896d655f4d4 ("bpf: introduce bpf_clone_redirect() helper")
  48 Fixes: 27b29f63058d ("bpf: add bpf_redirect() helper")
  49 Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
  50 Acked-by: Alexei Starovoitov <ast@kernel.org>
  51 Signed-off-by: David S. Miller <davem@davemloft.net>
  52 ---
  53  net/core/filter.c | 17 +++++++++++++----
  54  1 file changed, 13 insertions(+), 4 deletions(-)
  55
  56 --- a/net/core/filter.c
  57 +++ b/net/core/filter.c
  58 @@ -1293,8 +1293,9 @@ static u64 bpf_skb_store_bytes(u64 r1, u
  59                 /* skb_store_bits cannot return -EFAULT here */
  60                 skb_store_bits(skb, offset, ptr, len);
  61
  62 -       if (BPF_RECOMPUTE_CSUM(flags) && skb->ip_summed == CHECKSUM_COMPLETE)
  63 -               skb->csum = csum_add(skb->csum, csum_partial(ptr, len, 0));
  64 +       if (BPF_RECOMPUTE_CSUM(flags))
  65 +               skb_postpush_rcsum(skb, ptr, len);
  66 +
  67         return 0;
  68  }
  69
  70 @@ -1420,8 +1421,12 @@ static u64 bpf_clone_redirect(u64 r1, u6
  71         if (unlikely(!skb2))
  72                 return -ENOMEM;
  73
  74 -       if (BPF_IS_REDIRECT_INGRESS(flags))
  75 +       if (BPF_IS_REDIRECT_INGRESS(flags)) {
  76 +               if (skb_at_tc_ingress(skb2))
  77 +                       skb_postpush_rcsum(skb2, skb_mac_header(skb2),
  78 +                                          skb2->mac_len);
  79                 return dev_forward_skb(dev, skb2);
  80 +       }
  81
  82         skb2->dev = dev;
  83         skb_sender_cpu_clear(skb2);
  84 @@ -1464,8 +1469,12 @@ int skb_do_redirect(struct sk_buff *skb)
  85                 return -EINVAL;
  86         }
  87
  88 -       if (BPF_IS_REDIRECT_INGRESS(ri->flags))
  89 +       if (BPF_IS_REDIRECT_INGRESS(ri->flags)) {
  90 +               if (skb_at_tc_ingress(skb))
  91 +                       skb_postpush_rcsum(skb, skb_mac_header(skb),
  92 +                                          skb->mac_len);
  93                 return dev_forward_skb(dev, skb);
  94 +       }
  95
  96         skb->dev = dev;
  97         skb_sender_cpu_clear(skb);