From 14b5fb2145caeb909a1cd57d9cd5e0c3cd005642 Mon Sep 17 00:00:00 2001 From: Philo Lu Date: Sun, 21 Apr 2024 12:20:08 +0800 Subject: [PATCH 1/2] tcp: move tcp_skb_cb->sacked flags to enum Move the flag definitions for tcp_skb_cb->sacked into a new enum named tcp_skb_cb_sacked_flags, then we can get access to them in bpf via vmlinux.h, e.g., in tracepoints. This patch does not change any existing functionality. Signed-off-by: Philo Lu Reviewed-by: Eric Dumazet Signed-off-by: David S. Miller --- include/net/tcp.h | 22 +++++++++++++--------- 1 file changed, 13 insertions(+), 9 deletions(-) diff --git a/include/net/tcp.h b/include/net/tcp.h index b935e1ae4caf8..ffc9371fe9dea 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -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? */ From 2bf90a57f0e682872c5cfb66ffa45e432bb9c7ae Mon Sep 17 00:00:00 2001 From: Philo Lu Date: Sun, 21 Apr 2024 12:20:09 +0800 Subject: [PATCH 2/2] tcp: update sacked after tracepoint in __tcp_retransmit_skb Marking TCP_SKB_CB(skb)->sacked with TCPCB_EVER_RETRANS after the traceopint (trace_tcp_retransmit_skb), then we can get the retransmission efficiency by counting skbs w/ and w/o TCPCB_EVER_RETRANS mark in this tracepoint. 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: Philo Lu Reviewed-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv4/tcp_output.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 99a1d88f7f47b..ce59e4499b66d 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -3418,11 +3418,6 @@ int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs) 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 @@ int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs) } 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; }