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bpf: Add gso_size to __sk_buff 

BPF programs may want to know whether an skb is gso. The canonical
answer is skb_is_gso(skb), which tests that gso_size != 0.

Expose this field in the same manner as gso_segs. That field itself
is not a sufficient signal, as the comment in skb_shared_info makes
clear: gso_segs may be zero, e.g., from dodgy sources.

Also prepare net/bpf/test_run for upcoming BPF_PROG_TEST_RUN tests
of the feature.

Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200303200503.226217-2-willemdebruijn.kernel@gmail.com
This commit is contained in:
Willem de Bruijn 2020-03-03 15:05:01 -05:00 committed by Alexei Starovoitov
parent abbc61a5f2
commit cf62089b0e
3 changed files with 38 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/uapi/linux/bpf.h
View File

@ -3176,6 +3176,7 @@ struct __sk_buff {
__u32 wire_len;
__u32 gso_segs;
__bpf_md_ptr(struct bpf_sock *, sk);
__u32 gso_size;
};
struct bpf_tunnel_key {

7
net/bpf/test_run.c
View File

@ -277,6 +277,12 @@ static int convert___skb_to_skb(struct sk_buff *skb, struct __sk_buff *__skb)
/* gso_segs is allowed */
if (!range_is_zero(__skb, offsetofend(struct __sk_buff, gso_segs),
offsetof(struct __sk_buff, gso_size)))
return -EINVAL;
/* gso_size is allowed */
if (!range_is_zero(__skb, offsetofend(struct __sk_buff, gso_size),
sizeof(struct __sk_buff)))
return -EINVAL;
@ -297,6 +303,7 @@ static int convert___skb_to_skb(struct sk_buff *skb, struct __sk_buff *__skb)
if (__skb->gso_segs > GSO_MAX_SEGS)
return -EINVAL;
skb_shinfo(skb)->gso_segs = __skb->gso_segs;
skb_shinfo(skb)->gso_size = __skb->gso_size;
return 0;
}

44
net/core/filter.c
View File

@ -7139,6 +7139,27 @@ static u32 flow_dissector_convert_ctx_access(enum bpf_access_type type,
return insn - insn_buf;
}
static struct bpf_insn *bpf_convert_shinfo_access(const struct bpf_insn *si,
struct bpf_insn *insn)
{
/* si->dst_reg = skb_shinfo(SKB); */
#ifdef NET_SKBUFF_DATA_USES_OFFSET
*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_buff, end),
BPF_REG_AX, si->src_reg,
offsetof(struct sk_buff, end));
*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_buff, head),
si->dst_reg, si->src_reg,
offsetof(struct sk_buff, head));
*insn++ = BPF_ALU64_REG(BPF_ADD, si->dst_reg, BPF_REG_AX);
#else
*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_buff, end),
si->dst_reg, si->src_reg,
offsetof(struct sk_buff, end));
#endif
return insn;
}
static u32 bpf_convert_ctx_access(enum bpf_access_type type,
const struct bpf_insn *si,
struct bpf_insn *insn_buf,
@ -7461,26 +7482,21 @@ static u32 bpf_convert_ctx_access(enum bpf_access_type type,
break;
case offsetof(struct __sk_buff, gso_segs):
/* si->dst_reg = skb_shinfo(SKB); */
#ifdef NET_SKBUFF_DATA_USES_OFFSET
*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_buff, end),
BPF_REG_AX, si->src_reg,
offsetof(struct sk_buff, end));
*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_buff, head),
si->dst_reg, si->src_reg,
offsetof(struct sk_buff, head));
*insn++ = BPF_ALU64_REG(BPF_ADD, si->dst_reg, BPF_REG_AX);
#else
*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_buff, end),
si->dst_reg, si->src_reg,
offsetof(struct sk_buff, end));
#endif
insn = bpf_convert_shinfo_access(si, insn);
*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct skb_shared_info, gso_segs),
si->dst_reg, si->dst_reg,
bpf_target_off(struct skb_shared_info,
gso_segs, 2,
target_size));
break;
case offsetof(struct __sk_buff, gso_size):
insn = bpf_convert_shinfo_access(si, insn);
*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct skb_shared_info, gso_size),
si->dst_reg, si->dst_reg,
bpf_target_off(struct skb_shared_info,
gso_size, 2,
target_size));
break;
case offsetof(struct __sk_buff, wire_len):
BUILD_BUG_ON(sizeof_field(struct qdisc_skb_cb, pkt_len) != 4);