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bpf: allow BPF programs access skb->skb_iif and skb->dev->ifindex fields

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classic BPF already exposes skb->dev->ifindex via SKF_AD_IFINDEX extension.
Allow eBPF program to access it as well. Note that classic aborts execution
of the program if 'skb->dev == NULL' (which is inconvenient for program
writers), whereas eBPF returns zero in such case.
Also expose the 'skb_iif' field, since programs triggered by redirected
packet need to known the original interface index.
Summary:
__skb->ifindex         -> skb->dev->ifindex
__skb->ingress_ifindex -> skb->skb_iif

Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Alexei Starovoitov 2015-05-27 15:30:39 -07:00 committed by David S. Miller
parent e01ec2199e
commit 37e82c2f97
2 changed files with 20 additions and 0 deletions
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2
include/uapi/linux/bpf.h
View File

@ -236,6 +236,8 @@ struct __sk_buff {
__u32 vlan_tci;
__u32 vlan_proto;
__u32 priority;
__u32 ingress_ifindex;
__u32 ifindex;
};
#endif /* _UAPI__LINUX_BPF_H__ */

18
net/core/filter.c
View File

@ -1499,6 +1499,24 @@ static u32 sk_filter_convert_ctx_access(int dst_reg, int src_reg, int ctx_off,
offsetof(struct sk_buff, priority));
break;
case offsetof(struct __sk_buff, ingress_ifindex):
BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, skb_iif) != 4);
*insn++ = BPF_LDX_MEM(BPF_W, dst_reg, src_reg,
offsetof(struct sk_buff, skb_iif));
break;
case offsetof(struct __sk_buff, ifindex):
BUILD_BUG_ON(FIELD_SIZEOF(struct net_device, ifindex) != 4);
*insn++ = BPF_LDX_MEM(bytes_to_bpf_size(FIELD_SIZEOF(struct sk_buff, dev)),
dst_reg, src_reg,
offsetof(struct sk_buff, dev));
*insn++ = BPF_JMP_IMM(BPF_JEQ, dst_reg, 0, 1);
*insn++ = BPF_LDX_MEM(BPF_W, dst_reg, dst_reg,
offsetof(struct net_device, ifindex));
break;
case offsetof(struct __sk_buff, mark):
return convert_skb_access(SKF_AD_MARK, dst_reg, src_reg, insn);