From: Feng Zhou <zhoufeng.zf@xxxxxxxxxxxxx>
Set the full package write tcp option, the test found that the loss
will be 20%. If a package wants to write tcp option, it will trigger
bpf prog three times, and call "tcp_send_mss" calculate mss_cache,
call "tcp_established_options" to reserve tcp opt len, call
"bpf_skops_write_hdr_opt" to write tcp opt, but "tcp_send_mss" before
TSO. Through bpftrace tracking, it was found that during the pressure
test, "tcp_send_mss" call frequency was 90w/s. Considering that opt
len does not change often, consider caching opt len for optimization.
Signed-off-by: Feng Zhou <zhoufeng.zf@xxxxxxxxxxxxx>
---
include/linux/tcp.h | 3 +++
include/uapi/linux/bpf.h | 8 +++++++-
net/ipv4/tcp_output.c | 12 +++++++++++-
tools/include/uapi/linux/bpf.h | 8 +++++++-
4 files changed, 28 insertions(+), 3 deletions(-)
diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index 6a5e08b937b3..74437fcf94a2 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -455,6 +455,9 @@ struct tcp_sock {
* to recur itself by calling
* bpf_setsockopt(TCP_CONGESTION, "itself").
*/
+ u8 bpf_opt_len; /* save tcp opt len implementation
+ * BPF_SOCK_OPS_HDR_OPT_LEN_CB fast path
+ */
#define BPF_SOCK_OPS_TEST_FLAG(TP, ARG) (TP->bpf_sock_ops_cb_flags & ARG)
#else
#define BPF_SOCK_OPS_TEST_FLAG(TP, ARG) 0
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 90706a47f6ff..f2092de1f432 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -6892,8 +6892,14 @@ enum {
* options first before the BPF program does.
*/
BPF_SOCK_OPS_WRITE_HDR_OPT_CB_FLAG = (1<<6),
+ /* Fast path to reserve space in a skb under
+ * sock_ops->op == BPF_SOCK_OPS_HDR_OPT_LEN_CB.
+ * opt length doesn't change often, so it can save in the tcp_sock. And
+ * set BPF_SOCK_OPS_HDR_OPT_LEN_CACHE_CB_FLAG to no bpf call.
+ */
+ BPF_SOCK_OPS_HDR_OPT_LEN_CACHE_CB_FLAG = (1<<7),
/* Mask of all currently supported cb flags */
- BPF_SOCK_OPS_ALL_CB_FLAGS = 0x7F,
+ BPF_SOCK_OPS_ALL_CB_FLAGS = 0xFF,
};
/* List of known BPF sock_ops operators.
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index ea7ad7d99245..0e7480a58012 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -488,12 +488,21 @@ static void bpf_skops_hdr_opt_len(struct sock *sk, struct sk_buff *skb,
{
struct bpf_sock_ops_kern sock_ops;
int err;
+ struct tcp_sock *th = (struct tcp_sock *)sk;
- if (likely(!BPF_SOCK_OPS_TEST_FLAG(tcp_sk(sk),
+ if (likely(!BPF_SOCK_OPS_TEST_FLAG(th,
BPF_SOCK_OPS_WRITE_HDR_OPT_CB_FLAG)) ||
!*remaining)
return;
+ if (likely(BPF_SOCK_OPS_TEST_FLAG(th,
+ BPF_SOCK_OPS_HDR_OPT_LEN_CACHE_CB_FLAG)) &&
+ th->bpf_opt_len) {
+ *remaining -= th->bpf_opt_len;
+ opts->bpf_opt_len = th->bpf_opt_len;
+ return;
+ }
+
/* *remaining has already been aligned to 4 bytes, so *remaining >= 4 */
/* init sock_ops */
@@ -538,6 +547,7 @@ static void bpf_skops_hdr_opt_len(struct sock *sk, struct sk_buff *skb,
opts->bpf_opt_len = *remaining - sock_ops.remaining_opt_len;
/* round up to 4 bytes */
opts->bpf_opt_len = (opts->bpf_opt_len + 3) & ~3;
+ th->bpf_opt_len = opts->bpf_opt_len;
*remaining -= opts->bpf_opt_len;
}
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 90706a47f6ff..f2092de1f432 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -6892,8 +6892,14 @@ enum {
* options first before the BPF program does.
*/
BPF_SOCK_OPS_WRITE_HDR_OPT_CB_FLAG = (1<<6),
+ /* Fast path to reserve space in a skb under
+ * sock_ops->op == BPF_SOCK_OPS_HDR_OPT_LEN_CB.
+ * opt length doesn't change often, so it can save in the tcp_sock. And
+ * set BPF_SOCK_OPS_HDR_OPT_LEN_CACHE_CB_FLAG to no bpf call.
+ */
+ BPF_SOCK_OPS_HDR_OPT_LEN_CACHE_CB_FLAG = (1<<7),
/* Mask of all currently supported cb flags */
- BPF_SOCK_OPS_ALL_CB_FLAGS = 0x7F,
+ BPF_SOCK_OPS_ALL_CB_FLAGS = 0xFF,
};
/* List of known BPF sock_ops operators.
--
2.30.2
