* [PATCH net-next v2 1/2] net, sched: add skb_at_tc_ingress helper
2016-01-07 14:50 [PATCH net-next v2 0/2] BPF update Daniel Borkmann
@ 2016-01-07 14:50 ` Daniel Borkmann
2016-01-07 18:12 ` Alexei Starovoitov
2016-01-07 14:50 ` [PATCH net-next v2 2/2] bpf: add skb_postpush_rcsum and fix dev_forward_skb occasions Daniel Borkmann
2016-01-10 22:55 ` [PATCH net-next v2 0/2] BPF update David Miller
2 siblings, 1 reply; 6+ messages in thread
From: Daniel Borkmann @ 2016-01-07 14:50 UTC (permalink / raw)
To: davem; +Cc: alexei.starovoitov, hannes, netdev, Daniel Borkmann
Add a skb_at_tc_ingress() as this will be needed elsewhere as well and
can hide the ugly ifdef.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
---
include/net/sch_generic.h | 9 +++++++++
net/sched/cls_bpf.c | 6 +-----
2 files changed, 10 insertions(+), 5 deletions(-)
diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index b2a8e63..636a362 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -407,6 +407,15 @@ bool tcf_destroy(struct tcf_proto *tp, bool force);
void tcf_destroy_chain(struct tcf_proto __rcu **fl);
int skb_do_redirect(struct sk_buff *);
+static inline bool skb_at_tc_ingress(const struct sk_buff *skb)
+{
+#ifdef CONFIG_NET_CLS_ACT
+ return G_TC_AT(skb->tc_verd) & AT_INGRESS;
+#else
+ return false;
+#endif
+}
+
/* Reset all TX qdiscs greater then index of a device. */
static inline void qdisc_reset_all_tx_gt(struct net_device *dev, unsigned int i)
{
diff --git a/net/sched/cls_bpf.c b/net/sched/cls_bpf.c
index 99259f5..8dc8430 100644
--- a/net/sched/cls_bpf.c
+++ b/net/sched/cls_bpf.c
@@ -79,12 +79,8 @@ static int cls_bpf_classify(struct sk_buff *skb, const struct tcf_proto *tp,
struct tcf_result *res)
{
struct cls_bpf_head *head = rcu_dereference_bh(tp->root);
+ bool at_ingress = skb_at_tc_ingress(skb);
struct cls_bpf_prog *prog;
-#ifdef CONFIG_NET_CLS_ACT
- bool at_ingress = G_TC_AT(skb->tc_verd) & AT_INGRESS;
-#else
- bool at_ingress = false;
-#endif
int ret = -1;
if (unlikely(!skb_mac_header_was_set(skb)))
--
1.9.3
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH net-next v2 2/2] bpf: add skb_postpush_rcsum and fix dev_forward_skb occasions
2016-01-07 14:50 [PATCH net-next v2 0/2] BPF update Daniel Borkmann
2016-01-07 14:50 ` [PATCH net-next v2 1/2] net, sched: add skb_at_tc_ingress helper Daniel Borkmann
@ 2016-01-07 14:50 ` Daniel Borkmann
2016-01-07 18:52 ` Alexei Starovoitov
2016-01-10 22:55 ` [PATCH net-next v2 0/2] BPF update David Miller
2 siblings, 1 reply; 6+ messages in thread
From: Daniel Borkmann @ 2016-01-07 14:50 UTC (permalink / raw)
To: davem; +Cc: alexei.starovoitov, hannes, netdev, Daniel Borkmann
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 <daniel@iogearbox.net>
---
include/linux/skbuff.h | 17 +++++++++++++++++
net/core/filter.c | 17 +++++++++++++----
2 files changed, 30 insertions(+), 4 deletions(-)
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 6b6bd42..07f9ccd 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2805,6 +2805,23 @@ static inline void skb_postpull_rcsum(struct sk_buff *skb,
unsigned char *skb_pull_rcsum(struct sk_buff *skb, unsigned int len);
+static inline void skb_postpush_rcsum(struct sk_buff *skb,
+ const void *start, unsigned int len)
+{
+ /* For performing the reverse operation to skb_postpull_rcsum(),
+ * we can instead of ...
+ *
+ * skb->csum = csum_add(skb->csum, csum_partial(start, len, 0));
+ *
+ * ... just use this equivalent version here to save a few
+ * instructions. Feeding csum of 0 in csum_partial() and later
+ * on adding skb->csum is equivalent to feed skb->csum in the
+ * first place.
+ */
+ if (skb->ip_summed == CHECKSUM_COMPLETE)
+ skb->csum = csum_partial(start, len, skb->csum);
+}
+
/**
* pskb_trim_rcsum - trim received skb and update checksum
* @skb: buffer to trim
diff --git a/net/core/filter.c b/net/core/filter.c
index 35e6fed..0db92b5 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -1368,8 +1368,9 @@ static u64 bpf_skb_store_bytes(u64 r1, u64 r2, u64 r3, u64 r4, u64 flags)
/* 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;
}
@@ -1525,8 +1526,12 @@ static u64 bpf_clone_redirect(u64 r1, u64 ifindex, u64 flags, u64 r4, u64 r5)
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);
@@ -1569,8 +1574,12 @@ 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);
--
1.9.3
^ permalink raw reply related [flat|nested] 6+ messages in thread