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bpf: make skb->tc_classid also readable 

Currently, the tc_classid from eBPF skb context is write-only, but there's
no good reason for tc programs to limit it to write-only. For example,
it can be used to transfer its state via tail calls where the resulting
tc_classid gets filled gradually.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Daniel Borkmann 2016-03-16 01:42:49 +01:00 committed by David S. Miller
parent 019ded3aa7
commit 09c37a2c5b
1 changed files with 6 additions and 6 deletions
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12
net/core/filter.c
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@ -2069,16 +2069,14 @@ static bool sk_filter_is_valid_access(int off, int size,
static bool tc_cls_act_is_valid_access(int off, int size,
enum bpf_access_type type)
{
if (off == offsetof(struct __sk_buff, tc_classid))
return type == BPF_WRITE ? true : false;
if (type == BPF_WRITE) {
switch (off) {
case offsetof(struct __sk_buff, mark):
case offsetof(struct __sk_buff, tc_index):
case offsetof(struct __sk_buff, priority):
case offsetof(struct __sk_buff, cb[0]) ...
offsetof(struct __sk_buff, cb[4]):
offsetof(struct __sk_buff, cb[4]):
case offsetof(struct __sk_buff, tc_classid):
break;
default:
return false;
@ -2195,8 +2193,10 @@ static u32 bpf_net_convert_ctx_access(enum bpf_access_type type, int dst_reg,
ctx_off -= offsetof(struct __sk_buff, tc_classid);
ctx_off += offsetof(struct sk_buff, cb);
ctx_off += offsetof(struct qdisc_skb_cb, tc_classid);
WARN_ON(type != BPF_WRITE);
*insn++ = BPF_STX_MEM(BPF_H, dst_reg, src_reg, ctx_off);
if (type == BPF_WRITE)
*insn++ = BPF_STX_MEM(BPF_H, dst_reg, src_reg, ctx_off);
else
*insn++ = BPF_LDX_MEM(BPF_H, dst_reg, src_reg, ctx_off);
break;
case offsetof(struct __sk_buff, tc_index):