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- From 367956e87b62ae1f015ccbff58c7920a2e7a3511 Mon Sep 17 00:00:00 2001
- From: Daniel Borkmann <[email protected]>
- Date: Thu, 7 Jan 2016 15:50:23 +0100
- Subject: [PATCH 221/423] bpf: add skb_postpush_rcsum and fix dev_forward_skb
- occasions
- Add a small helper skb_postpush_rcsum() and fix up redirect locations
- that need CHECKSUM_COMPLETE fixups on ingress. dev_forward_skb() expects
- a proper csum that covers also Ethernet header, f.e. since 2c26d34bbcc0
- ("net/core: Handle csum for CHECKSUM_COMPLETE VXLAN forwarding"), we
- also do skb_postpull_rcsum() after pulling Ethernet header off via
- eth_type_trans().
- When using eBPF in a netns setup f.e. with vxlan in collect metadata mode,
- I can trigger the following csum issue with an IPv6 setup:
- [ 505.144065] dummy1: hw csum failure
- [...]
- [ 505.144108] Call Trace:
- [ 505.144112] <IRQ> [<ffffffff81372f08>] dump_stack+0x44/0x5c
- [ 505.144134] [<ffffffff81607cea>] netdev_rx_csum_fault+0x3a/0x40
- [ 505.144142] [<ffffffff815fee3f>] __skb_checksum_complete+0xcf/0xe0
- [ 505.144149] [<ffffffff816f0902>] nf_ip6_checksum+0xb2/0x120
- [ 505.144161] [<ffffffffa08c0e0e>] icmpv6_error+0x17e/0x328 [nf_conntrack_ipv6]
- [ 505.144170] [<ffffffffa0898eca>] ? ip6t_do_table+0x2fa/0x645 [ip6_tables]
- [ 505.144177] [<ffffffffa08c0725>] ? ipv6_get_l4proto+0x65/0xd0 [nf_conntrack_ipv6]
- [ 505.144189] [<ffffffffa06c9a12>] nf_conntrack_in+0xc2/0x5a0 [nf_conntrack]
- [ 505.144196] [<ffffffffa08c039c>] ipv6_conntrack_in+0x1c/0x20 [nf_conntrack_ipv6]
- [ 505.144204] [<ffffffff8164385d>] nf_iterate+0x5d/0x70
- [ 505.144210] [<ffffffff816438d6>] nf_hook_slow+0x66/0xc0
- [ 505.144218] [<ffffffff816bd302>] ipv6_rcv+0x3f2/0x4f0
- [ 505.144225] [<ffffffff816bca40>] ? ip6_make_skb+0x1b0/0x1b0
- [ 505.144232] [<ffffffff8160b77b>] __netif_receive_skb_core+0x36b/0x9a0
- [ 505.144239] [<ffffffff8160bdc8>] ? __netif_receive_skb+0x18/0x60
- [ 505.144245] [<ffffffff8160bdc8>] __netif_receive_skb+0x18/0x60
- [ 505.144252] [<ffffffff8160ccff>] process_backlog+0x9f/0x140
- [ 505.144259] [<ffffffff8160c4a5>] net_rx_action+0x145/0x320
- [...]
- What happens is that on ingress, we push Ethernet header back in, either
- from cls_bpf or right before skb_do_redirect(), but without updating csum.
- The "hw csum failure" can be fixed by using the new skb_postpush_rcsum()
- helper for the dev_forward_skb() case to correct the csum diff again.
- Thanks to Hannes Frederic Sowa for the csum_partial() idea!
- Fixes: 3896d655f4d4 ("bpf: introduce bpf_clone_redirect() helper")
- Fixes: 27b29f63058d ("bpf: add bpf_redirect() helper")
- Signed-off-by: Daniel Borkmann <[email protected]>
- Acked-by: Alexei Starovoitov <[email protected]>
- Signed-off-by: David S. Miller <[email protected]>
- ---
- net/core/filter.c | 17 +++++++++++++----
- 1 file changed, 13 insertions(+), 4 deletions(-)
- --- a/net/core/filter.c
- +++ b/net/core/filter.c
- @@ -1291,8 +1291,9 @@ static u64 bpf_skb_store_bytes(u64 r1, u
- /* skb_store_bits cannot return -EFAULT here */
- skb_store_bits(skb, offset, ptr, len);
-
- - if (BPF_RECOMPUTE_CSUM(flags) && skb->ip_summed == CHECKSUM_COMPLETE)
- - skb->csum = csum_add(skb->csum, csum_partial(ptr, len, 0));
- + if (BPF_RECOMPUTE_CSUM(flags))
- + skb_postpush_rcsum(skb, ptr, len);
- +
- return 0;
- }
-
- @@ -1415,8 +1416,12 @@ static u64 bpf_clone_redirect(u64 r1, u6
- if (unlikely(!skb2))
- return -ENOMEM;
-
- - if (BPF_IS_REDIRECT_INGRESS(flags))
- + if (BPF_IS_REDIRECT_INGRESS(flags)) {
- + if (skb_at_tc_ingress(skb2))
- + skb_postpush_rcsum(skb2, skb_mac_header(skb2),
- + skb2->mac_len);
- return dev_forward_skb(dev, skb2);
- + }
-
- skb2->dev = dev;
- skb_sender_cpu_clear(skb2);
- @@ -1459,8 +1464,12 @@ int skb_do_redirect(struct sk_buff *skb)
- return -EINVAL;
- }
-
- - if (BPF_IS_REDIRECT_INGRESS(ri->flags))
- + if (BPF_IS_REDIRECT_INGRESS(ri->flags)) {
- + if (skb_at_tc_ingress(skb))
- + skb_postpush_rcsum(skb, skb_mac_header(skb),
- + skb->mac_len);
- return dev_forward_skb(dev, skb);
- + }
-
- skb->dev = dev;
- skb_sender_cpu_clear(skb);
|
