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[RFC,net-next,2/2] TCP: pass accepted-TFO indication through getsockopt

Message ID 3e9b638ad6846aff954a590dd87f764684a4ec8f.1741877016.git.jgh@exim.org (mailing list archive)
State RFC
Delegated to: Netdev Maintainers
Headers show
Series TCP: Fast-Open observability | expand

Checks

Context Check Description
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for net-next, async
netdev/ynl success Generated files up to date; no warnings/errors; no diff in generated;
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 12 this patch: 12
netdev/build_tools success Errors and warnings before: 26 (+0) this patch: 26 (+0)
netdev/cc_maintainers fail 7 maintainers not CCed: edumazet@google.com kuniyu@amazon.com pabeni@redhat.com dsahern@kernel.org ncardwell@google.com horms@kernel.org kuba@kernel.org
netdev/build_clang success Errors and warnings before: 24 this patch: 24
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 2052 this patch: 2052
netdev/checkpatch warning WARNING: Missing commit description - Add an appropriate one
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 1 this patch: 1
netdev/source_inline success Was 0 now: 0

Commit Message

Jeremy Harris March 13, 2025, 2:45 p.m. UTC 
Signed-off-by: Jeremy Harris <jgh@exim.org>
---
 include/uapi/linux/tcp.h | 1 +
 net/ipv4/tcp.c           | 2 ++
 2 files changed, 3 insertions(+)
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Patch

diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h
index 32a27b4a5..e958a145d 100644
--- a/include/uapi/linux/tcp.h
+++ b/include/uapi/linux/tcp.h
@@ -179,6 +179,7 @@  enum tcp_fastopen_client_fail {
 #define TCPI_OPT_ECN_SEEN	16 /* we received at least one packet with ECT */
 #define TCPI_OPT_SYN_DATA	32 /* SYN-ACK acked data in SYN sent or rcvd */
 #define TCPI_OPT_USEC_TS	64 /* usec timestamps */
+#define TCPI_OPT_TFO_SEEN	128 /* we accepted a Fast Open option on SYN */
 
 /*
  * Sender's congestion state indicating normal or abnormal situations
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 46951e749..407bdfb12 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -4146,6 +4146,8 @@  void tcp_get_info(struct sock *sk, struct tcp_info *info)
 		info->tcpi_options |= TCPI_OPT_SYN_DATA;
 	if (tp->tcp_usec_ts)
 		info->tcpi_options |= TCPI_OPT_USEC_TS;
+	if (tp->syn_fastopen_in)
+		info->tcpi_options |= TCPI_OPT_TFO_SEEN;
 
 	info->tcpi_rto = jiffies_to_usecs(icsk->icsk_rto);
 	info->tcpi_ato = jiffies_to_usecs(min_t(u32, icsk->icsk_ack.ato,