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bpf: Add hwtstamp field for the sockops prog

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The bpf-tc prog has already been able to access the
skb_hwtstamps(skb)->hwtstamp.  This patch extends the same hwtstamp
access to the sockops prog.

In sockops, the skb is also available to the bpf prog during
the BPF_SOCK_OPS_PARSE_HDR_OPT_CB event.  There is a use case
that the hwtstamp will be useful to the sockops prog to better
measure the one-way-delay when the sender has put the tx
timestamp in the tcp header option.

Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20221107230420.4192307-2-martin.lau@linux.dev
This commit is contained in:
Martin KaFai Lau 2022-11-07 15:04:18 -08:00 committed by Andrii Nakryiko
parent e4c9cf0ce8
commit 9bb053490f
3 changed files with 33 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

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

@ -6445,6 +6445,7 @@ struct bpf_sock_ops {
* the outgoing header has not
* been written yet.
*/
__u64 skb_hwtstamp;
};
/* Definitions for bpf_sock_ops_cb_flags */

39
net/core/filter.c
View File

@ -8925,6 +8925,10 @@ static bool sock_ops_is_valid_access(int off, int size,
bpf_ctx_record_field_size(info, size_default);
return bpf_ctx_narrow_access_ok(off, size,
size_default);
case offsetof(struct bpf_sock_ops, skb_hwtstamp):
if (size != sizeof(__u64))
return false;
break;
default:
if (size != size_default)
return false;
@ -9108,21 +9112,21 @@ static struct bpf_insn *bpf_convert_tstamp_type_read(const struct bpf_insn *si,
return insn;
}
static struct bpf_insn *bpf_convert_shinfo_access(const struct bpf_insn *si,
static struct bpf_insn *bpf_convert_shinfo_access(__u8 dst_reg, __u8 skb_reg,
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,
BPF_REG_AX, skb_reg,
offsetof(struct sk_buff, end));
*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_buff, head),
si->dst_reg, si->src_reg,
dst_reg, skb_reg,
offsetof(struct sk_buff, head));
*insn++ = BPF_ALU64_REG(BPF_ADD, si->dst_reg, BPF_REG_AX);
*insn++ = BPF_ALU64_REG(BPF_ADD, dst_reg, BPF_REG_AX);
#else
*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_buff, end),
si->dst_reg, si->src_reg,
dst_reg, skb_reg,
offsetof(struct sk_buff, end));
#endif
@ -9515,7 +9519,7 @@ static u32 bpf_convert_ctx_access(enum bpf_access_type type,
break;
case offsetof(struct __sk_buff, gso_segs):
insn = bpf_convert_shinfo_access(si, insn);
insn = bpf_convert_shinfo_access(si->dst_reg, si->src_reg, 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,
@ -9523,7 +9527,7 @@ static u32 bpf_convert_ctx_access(enum bpf_access_type type,
target_size));
break;
case offsetof(struct __sk_buff, gso_size):
insn = bpf_convert_shinfo_access(si, insn);
insn = bpf_convert_shinfo_access(si->dst_reg, si->src_reg, 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,
@ -9550,7 +9554,7 @@ static u32 bpf_convert_ctx_access(enum bpf_access_type type,
BUILD_BUG_ON(sizeof_field(struct skb_shared_hwtstamps, hwtstamp) != 8);
BUILD_BUG_ON(offsetof(struct skb_shared_hwtstamps, hwtstamp) != 0);
insn = bpf_convert_shinfo_access(si, insn);
insn = bpf_convert_shinfo_access(si->dst_reg, si->src_reg, insn);
*insn++ = BPF_LDX_MEM(BPF_DW,
si->dst_reg, si->dst_reg,
bpf_target_off(struct skb_shared_info,
@ -10400,6 +10404,25 @@ static u32 sock_ops_convert_ctx_access(enum bpf_access_type type,
tcp_flags),
si->dst_reg, si->dst_reg, off);
break;
case offsetof(struct bpf_sock_ops, skb_hwtstamp): {
struct bpf_insn *jmp_on_null_skb;
*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct bpf_sock_ops_kern,
skb),
si->dst_reg, si->src_reg,
offsetof(struct bpf_sock_ops_kern,
skb));
/* Reserve one insn to test skb == NULL */
jmp_on_null_skb = insn++;
insn = bpf_convert_shinfo_access(si->dst_reg, si->dst_reg, insn);
*insn++ = BPF_LDX_MEM(BPF_DW, si->dst_reg, si->dst_reg,
bpf_target_off(struct skb_shared_info,
hwtstamps, 8,
target_size));
*jmp_on_null_skb = BPF_JMP_IMM(BPF_JEQ, si->dst_reg, 0,
insn - jmp_on_null_skb - 1);
break;
}
}
return insn - insn_buf;
}

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

@ -6445,6 +6445,7 @@ struct bpf_sock_ops {
* the outgoing header has not
* been written yet.
*/
__u64 skb_hwtstamp;
};
/* Definitions for bpf_sock_ops_cb_flags */