Based on comments by Neal Cardwell to tcp_nv patch:
AFAICT this patch would not require an increase in the size of sk_buff
cb[] if it were to take advantage of the fact that the tcp_skb_cb
header.h4 and header.h6 fields are only used in the packet reception
code path, and this in_flight field is only used on the transmit
side. So the in_flight field could be placed in a struct that is
itself placed in a union with the "header" union.
That way the sender code can remember the in_flight value
without requiring any extra space. And in the future other
sender-side info could be stored in the "tx" struct, if needed.
Signed-off-by: Lawrence Brakmo <bra...@fb.com>
---
include/net/tcp.h | 13 ++++++++++---
net/ipv4/tcp_input.c | 5 ++++-
net/ipv4/tcp_output.c | 4 +++-
3 files changed, 17 insertions(+), 5 deletions(-)
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 1e6c5b04..b98d79a 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -755,11 +755,17 @@ struct tcp_skb_cb {
/* 1 byte hole */
__u32 ack_seq; /* Sequence number ACK'd */
union {
- struct inet_skb_parm h4;
+ struct {
+ /* bytes in flight when this packet was sent */
+ __u32 in_flight;
+ } tx; /* only used for outgoing skbs */
+ union {
+ struct inet_skb_parm h4;
#if IS_ENABLED(CONFIG_IPV6)
- struct inet6_skb_parm h6;
+ struct inet6_skb_parm h6;
#endif
- } header; /* For incoming frames */
+ } header; /* For incoming skbs */
+ };
};
#define TCP_SKB_CB(__skb) ((struct tcp_skb_cb *)&((__skb)->cb[0]))
@@ -837,6 +843,7 @@ union tcp_cc_info;
struct ack_sample {
u32 pkts_acked;
s32 rtt_us;
+ u32 in_flight;
};
struct tcp_congestion_ops {
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 423d3af..3ab4178 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3068,6 +3068,7 @@ static int tcp_clean_rtx_queue(struct sock *sk, int
prior_fackets,
long ca_rtt_us = -1L;
struct sk_buff *skb;
u32 pkts_acked = 0;
+ u32 last_in_flight = 0;
bool rtt_update;
int flag = 0;
@@ -3107,6 +3108,7 @@ static int tcp_clean_rtx_queue(struct sock *sk, int
prior_fackets,
if (!first_ackt.v64)
first_ackt = last_ackt;
+ last_in_flight = TCP_SKB_CB(skb)->tx.in_flight;
reord = min(pkts_acked, reord);
if (!after(scb->end_seq, tp->high_seq))
flag |= FLAG_ORIG_SACK_ACKED;
@@ -3196,7 +3198,8 @@ static int tcp_clean_rtx_queue(struct sock *sk, int
prior_fackets,
}
if (icsk->icsk_ca_ops->pkts_acked) {
- struct ack_sample sample = {pkts_acked, ca_rtt_us};
+ struct ack_sample sample = {pkts_acked, ca_rtt_us,
+ last_in_flight};
icsk->icsk_ca_ops->pkts_acked(sk, &sample);
}
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 7105784..e9deab5 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -920,9 +920,12 @@ static int tcp_transmit_skb(struct sock *sk, struct
sk_buff *skb, int clone_it,
int err;
BUG_ON(!skb || !tcp_skb_pcount(skb));
+ tp = tcp_sk(sk);
if (clone_it) {
skb_mstamp_get(&skb->skb_mstamp);
+ TCP_SKB_CB(skb)->tx.in_flight = TCP_SKB_CB(skb)->end_seq
+ - tp->snd_una;
if (unlikely(skb_cloned(skb)))
skb = pskb_copy(skb, gfp_mask);
@@ -933,7 +936,6 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff
*skb, int clone_it,
}
inet = inet_sk(sk);
- tp = tcp_sk(sk);
tcb = TCP_SKB_CB(skb);
memset(&opts, 0, sizeof(opts));
--
1.8.1
--
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