diff options
| author | Daniel Sedlak <daniel.sedlak@cdn77.com> | 2026-01-05 12:55:33 +0100 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2026-01-06 17:35:17 -0800 |
| commit | 55ffb0b14a4d310390ea2dd5a92e6d2e5c80d0ef (patch) | |
| tree | ea7ad385fe74bc6448ba5eb0ec3a1bdefbaf9df5 /include | |
| parent | f66086798f91f095ce377ca4f3d2765e305a842e (diff) | |
tcp: clarify tcp_congestion_ops functions comments
The optional and required hints in the tcp_congestion_ops are information
for the user of this interface to signalize its importance when
implementing these functions.
However, cong_avoid comment incorrectly tells that it is required,
in reality congestion control must provide one of either cong_avoid or
cong_control.
In addition, min_tso_segs has not had any comment optional/required
hints. So mark it as optional since it is used only in BBR.
Co-developed-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Daniel Sedlak <daniel.sedlak@cdn77.com>
Link: https://patch.msgid.link/20260105115533.1151442-1-daniel.sedlak@cdn77.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/net/tcp.h | 29 |
1 files changed, 19 insertions, 10 deletions
diff --git a/include/net/tcp.h b/include/net/tcp.h index 0deb5e9dd911..ef0fee58fde8 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -1243,12 +1243,27 @@ struct rate_sample { struct tcp_congestion_ops { /* fast path fields are put first to fill one cache line */ + /* A congestion control (CC) must provide one of either: + * + * (a) a cong_avoid function, if the CC wants to use the core TCP + * stack's default functionality to implement a "classic" + * (Reno/CUBIC-style) response to packet loss, RFC3168 ECN, + * idle periods, pacing rate computations, etc. + * + * (b) a cong_control function, if the CC wants custom behavior and + * complete control of all congestion control behaviors. + */ + /* (a) "classic" response: calculate new cwnd. + */ + void (*cong_avoid)(struct sock *sk, u32 ack, u32 acked); + /* (b) "custom" response: call when packets are delivered to update + * cwnd and pacing rate, after all the ca_state processing. + */ + void (*cong_control)(struct sock *sk, u32 ack, int flag, const struct rate_sample *rs); + /* return slow start threshold (required) */ u32 (*ssthresh)(struct sock *sk); - /* do new cwnd calculation (required) */ - void (*cong_avoid)(struct sock *sk, u32 ack, u32 acked); - /* call before changing ca_state (optional) */ void (*set_state)(struct sock *sk, u8 new_state); @@ -1261,15 +1276,9 @@ struct tcp_congestion_ops { /* hook for packet ack accounting (optional) */ void (*pkts_acked)(struct sock *sk, const struct ack_sample *sample); - /* override sysctl_tcp_min_tso_segs */ + /* override sysctl_tcp_min_tso_segs (optional) */ u32 (*min_tso_segs)(struct sock *sk); - /* call when packets are delivered to update cwnd and pacing rate, - * after all the ca_state processing. (optional) - */ - void (*cong_control)(struct sock *sk, u32 ack, int flag, const struct rate_sample *rs); - - /* new value of cwnd after loss (required) */ u32 (*undo_cwnd)(struct sock *sk); /* returns the multiplier used in tcp_sndbuf_expand (optional) */ |