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bpf: Add struct bpf_tcp_sock and BPF_FUNC_tcp_sock

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This patch adds a helper function BPF_FUNC_tcp_sock and it
is currently available for cg_skb and sched_(cls|act):

struct bpf_tcp_sock *bpf_tcp_sock(struct bpf_sock *sk);

int cg_skb_foo(struct __sk_buff *skb) {
	struct bpf_tcp_sock *tp;
	struct bpf_sock *sk;
	__u32 snd_cwnd;

	sk = skb->sk;
	if (!sk)
		return 1;

	tp = bpf_tcp_sock(sk);
	if (!tp)
		return 1;

	snd_cwnd = tp->snd_cwnd;
	/* ... */

	return 1;
}

A 'struct bpf_tcp_sock' is also added to the uapi bpf.h to provide
read-only access.  bpf_tcp_sock has all the existing tcp_sock's fields
that has already been exposed by the bpf_sock_ops.
i.e. no new tcp_sock's fields are exposed in bpf.h.

This helper returns a pointer to the tcp_sock.  If it is not a tcp_sock
or it cannot be traced back to a tcp_sock by sk_to_full_sk(), it
returns NULL.  Hence, the caller needs to check for NULL before
accessing it.

The current use case is to expose members from tcp_sock
to allow a cg_skb_bpf_prog to provide per cgroup traffic
policing/shaping.

Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Martin KaFai Lau
2019-02-09 23:22:24 -08:00
committed by Alexei Starovoitov
parent 9b1f3d6e5a
commit 655a51e536
4 changed files with 188 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

51
include/uapi/linux/bpf.h
View File

@@ -2337,6 +2337,15 @@ union bpf_attr {
* Return
* A **struct bpf_sock** pointer on success, or NULL in
* case of failure.
*
* struct bpf_tcp_sock *bpf_tcp_sock(struct bpf_sock *sk)
* Description
* This helper gets a **struct bpf_tcp_sock** pointer from a
* **struct bpf_sock** pointer.
*
* Return
* A **struct bpf_tcp_sock** pointer on success, or NULL in
* case of failure.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -2434,7 +2443,8 @@ union bpf_attr {
FN(rc_pointer_rel), \
FN(spin_lock), \
FN(spin_unlock), \
FN(sk_fullsock),
FN(sk_fullsock), \
FN(tcp_sock),
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
* function eBPF program intends to call
@@ -2616,6 +2626,45 @@ struct bpf_sock {
__u32 state;
};
struct bpf_tcp_sock {
__u32 snd_cwnd; /* Sending congestion window */
__u32 srtt_us; /* smoothed round trip time << 3 in usecs */
__u32 rtt_min;
__u32 snd_ssthresh; /* Slow start size threshold */
__u32 rcv_nxt; /* What we want to receive next */
__u32 snd_nxt; /* Next sequence we send */
__u32 snd_una; /* First byte we want an ack for */
__u32 mss_cache; /* Cached effective mss, not including SACKS */
__u32 ecn_flags; /* ECN status bits. */
__u32 rate_delivered; /* saved rate sample: packets delivered */
__u32 rate_interval_us; /* saved rate sample: time elapsed */
__u32 packets_out; /* Packets which are "in flight" */
__u32 retrans_out; /* Retransmitted packets out */
__u32 total_retrans; /* Total retransmits for entire connection */
__u32 segs_in; /* RFC4898 tcpEStatsPerfSegsIn
* total number of segments in.
*/
__u32 data_segs_in; /* RFC4898 tcpEStatsPerfDataSegsIn
* total number of data segments in.
*/
__u32 segs_out; /* RFC4898 tcpEStatsPerfSegsOut
* The total number of segments sent.
*/
__u32 data_segs_out; /* RFC4898 tcpEStatsPerfDataSegsOut
* total number of data segments sent.
*/
__u32 lost_out; /* Lost packets */
__u32 sacked_out; /* SACK'd packets */
__u64 bytes_received; /* RFC4898 tcpEStatsAppHCThruOctetsReceived
* sum(delta(rcv_nxt)), or how many bytes
* were acked.
*/
__u64 bytes_acked; /* RFC4898 tcpEStatsAppHCThruOctetsAcked
* sum(delta(snd_una)), or how many bytes
* were acked.
*/
};
struct bpf_sock_tuple {
union {
struct {