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Merge branch 'tcp-trace-next'

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Philo Lu says:

====================
tcp: update TCPCB_EVER_RETRANS after trace_tcp_retransmit_skb()

Move TCPCB_EVER_RETRANS updating after the trace_tcp_retransmit_skb()
in __tcp_retransmit_skb(), and then we are aware of whether the skb has
ever been retransmitted in this tracepoint. This can be used, e.g., to get
retransmission efficiency by counting skbs w/ and w/o TCPCB_EVER_RETRANS
(through bpf tracing programs).

For this purpose, TCPCB_EVER_RETRANS is also needed to be exposed to bpf.
Previously, the flags are defined as macros in struct tcp_skb_cb. I moved them
out into a new enum, and then they can be accessed with vmlinux.h.

We have discussed to achieve this with BPF_SOCK_OPS in [0], and using
tracepoint is thought to be a better solution.

[0]
https://lore.kernel.org/all/20240417124622.35333-1-lulie@linux.alibaba.com/
====================

Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller
2024-04-25 08:52:12 +01:00
parent d806871612 2bf90a57f0
commit caf93883f6
2 changed files with 19 additions and 14 deletions
Download Patch File Download Diff File Expand all files Collapse all files
include/net/tcp.h
+13 -9
View File
@@ -928,6 +928,19 @@ static inline u32 tcp_rsk_tsval(const struct tcp_request_sock *treq)
#define TCPHDR_SYN_ECN (TCPHDR_SYN | TCPHDR_ECE | TCPHDR_CWR)
/* State flags for sacked in struct tcp_skb_cb */
enum tcp_skb_cb_sacked_flags {
TCPCB_SACKED_ACKED = (1 << 0), /* SKB ACK'd by a SACK block */
TCPCB_SACKED_RETRANS = (1 << 1), /* SKB retransmitted */
TCPCB_LOST = (1 << 2), /* SKB is lost */
TCPCB_TAGBITS = (TCPCB_SACKED_ACKED | TCPCB_SACKED_RETRANS |
TCPCB_LOST), /* All tag bits */
TCPCB_REPAIRED = (1 << 4), /* SKB repaired (no skb_mstamp_ns) */
TCPCB_EVER_RETRANS = (1 << 7), /* Ever retransmitted frame */
TCPCB_RETRANS = (TCPCB_SACKED_RETRANS | TCPCB_EVER_RETRANS |
TCPCB_REPAIRED),
};
/* This is what the send packet queuing engine uses to pass
* TCP per-packet control information to the transmission code.
* We also store the host-order sequence numbers in here too.
@@ -950,15 +963,6 @@ struct tcp_skb_cb {
__u8 tcp_flags; /* TCP header flags. (tcp[13]) */
__u8 sacked; /* State flags for SACK. */
#define TCPCB_SACKED_ACKED 0x01 /* SKB ACK'd by a SACK block */
#define TCPCB_SACKED_RETRANS 0x02 /* SKB retransmitted */
#define TCPCB_LOST 0x04 /* SKB is lost */
#define TCPCB_TAGBITS 0x07 /* All tag bits */
#define TCPCB_REPAIRED 0x10 /* SKB repaired (no skb_mstamp_ns) */
#define TCPCB_EVER_RETRANS 0x80 /* Ever retransmitted frame */
#define TCPCB_RETRANS (TCPCB_SACKED_RETRANS|TCPCB_EVER_RETRANS| \
TCPCB_REPAIRED)
__u8 ip_dsfield; /* IPv4 tos or IPv6 dsfield */
__u8 txstamp_ack:1, /* Record TX timestamp for ack? */
eor:1, /* Is skb MSG_EOR marked? */
net/ipv4/tcp_output.c
+6 -5
View File
@@ -3418,11 +3418,6 @@ start:
err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
}
/* To avoid taking spuriously low RTT samples based on a timestamp
* for a transmit that never happened, always mark EVER_RETRANS
*/
TCP_SKB_CB(skb)->sacked |= TCPCB_EVER_RETRANS;
if (BPF_SOCK_OPS_TEST_FLAG(tp, BPF_SOCK_OPS_RETRANS_CB_FLAG))
tcp_call_bpf_3arg(sk, BPF_SOCK_OPS_RETRANS_CB,
TCP_SKB_CB(skb)->seq, segs, err);
@@ -3432,6 +3427,12 @@ start:
} else if (err != -EBUSY) {
NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPRETRANSFAIL, segs);
}
/* To avoid taking spuriously low RTT samples based on a timestamp
* for a transmit that never happened, always mark EVER_RETRANS
*/
TCP_SKB_CB(skb)->sacked |= TCPCB_EVER_RETRANS;
return err;
}