Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
Merge branch 'tcp-fastopen-observability'
Jeremy Harris says:
====================
tcp: fastopen: observability
Whether TCP Fast Open was used for a connection is not reliably
observable by an accepting application when the SYN passed no data.
Fix this by noting during SYN receive processing that an acceptable Fast
Open option was used, and provide this to userland via getsockopt TCP_INFO.
====================
Link: https://patch.msgid.link/20250423124334.4916-1-jgh@exim.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
+7
-1
+2
-1
include/linux/tcp.h
+2
-1
include/linux/tcp.h
···
385
385
syn_fastopen:1, /* SYN includes Fast Open option */
386
386
syn_fastopen_exp:1,/* SYN includes Fast Open exp. option */
387
387
syn_fastopen_ch:1, /* Active TFO re-enabling probe */
388
-
syn_data_acked:1;/* data in SYN is acked by SYN-ACK */
388
+
syn_data_acked:1,/* data in SYN is acked by SYN-ACK */
389
+
syn_fastopen_child:1; /* created TFO passive child socket */
389
390
390
391
u8 keepalive_probes; /* num of allowed keep alive probes */
391
392
u32 tcp_tx_delay; /* delay (in usec) added to TX packets */
+1
include/uapi/linux/tcp.h
+1
include/uapi/linux/tcp.h
···
184
184
#define TCPI_OPT_ECN_SEEN 16 /* we received at least one packet with ECT */
185
185
#define TCPI_OPT_SYN_DATA 32 /* SYN-ACK acked data in SYN sent or rcvd */
186
186
#define TCPI_OPT_USEC_TS 64 /* usec timestamps */
187
+
#define TCPI_OPT_TFO_CHILD 128 /* child from a Fast Open option on SYN */
187
188
188
189
/*
189
190
* Sender's congestion state indicating normal or abnormal situations
+3
net/ipv4/tcp.c
+3
net/ipv4/tcp.c
···
3409
3409
tp->rack.reo_wnd_persist = 0;
3410
3410
tp->rack.dsack_seen = 0;
3411
3411
tp->syn_data_acked = 0;
3412
+
tp->syn_fastopen_child = 0;
3412
3413
tp->rx_opt.saw_tstamp = 0;
3413
3414
tp->rx_opt.dsack = 0;
3414
3415
tp->rx_opt.num_sacks = 0;
···
4165
4164
info->tcpi_options |= TCPI_OPT_SYN_DATA;
4166
4165
if (tp->tcp_usec_ts)
4167
4166
info->tcpi_options |= TCPI_OPT_USEC_TS;
4167
+
if (tp->syn_fastopen_child)
4168
+
info->tcpi_options |= TCPI_OPT_TFO_CHILD;
4168
4169
4169
4170
info->tcpi_rto = jiffies_to_usecs(icsk->icsk_rto);
4170
4171
info->tcpi_ato = jiffies_to_usecs(min_t(u32, icsk->icsk_ack.ato,