Subject: [PATCH bpf v2 4/4] bpf: Fix documentation of th_len in bpf_tcp_{gen,check}_syncookie

From: Maxim Mikityanskiy <[email-masked]>
Date: Mon, 24 Jan 2022 17:11:46 +0200

bpf_tcp_gen_syncookie and bpf_tcp_check_syncookie expect the full length
of the TCP header (with all extensions). Fix the documentation that says
it should be sizeof(struct tcphdr).

Fixes: 399040847084 ("bpf: add helper to check for a valid SYN cookie")
Fixes: 70d66244317e ("bpf: add bpf_tcp_gen_syncookie helper")
Signed-off-by: Maxim Mikityanskiy <[email-masked]>
Reviewed-by: Tariq Toukan <[email-masked]>
---
 include/uapi/linux/bpf.h       | 6 ++++--
 tools/include/uapi/linux/bpf.h | 6 ++++--
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index b0383d371b9a..520f1e557dce 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -3553,7 +3553,8 @@ union bpf_attr {
  * 		**sizeof**\ (**struct ip6hdr**).
  *
  * 		*th* points to the start of the TCP header, while *th_len*
- * 		contains **sizeof**\ (**struct tcphdr**).
+ *		contains the length of the TCP header (at least
+ *		**sizeof**\ (**struct tcphdr**)).
  * 	Return
  * 		0 if *iph* and *th* are a valid SYN cookie ACK, or a negative
  * 		error otherwise.
@@ -3739,7 +3740,8 @@ union bpf_attr {
  *		**sizeof**\ (**struct ip6hdr**).
  *
  *		*th* points to the start of the TCP header, while *th_len*
- *		contains the length of the TCP header.
+ *		contains the length of the TCP header (at least
+ *		**sizeof**\ (**struct tcphdr**)).
  *	Return
  *		On success, lower 32 bits hold the generated SYN cookie in
  *		followed by 16 bits which hold the MSS value for that cookie,
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index b0383d371b9a..520f1e557dce 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -3553,7 +3553,8 @@ union bpf_attr {
  * 		**sizeof**\ (**struct ip6hdr**).
  *
  * 		*th* points to the start of the TCP header, while *th_len*
- * 		contains **sizeof**\ (**struct tcphdr**).
+ *		contains the length of the TCP header (at least
+ *		**sizeof**\ (**struct tcphdr**)).
  * 	Return
  * 		0 if *iph* and *th* are a valid SYN cookie ACK, or a negative
  * 		error otherwise.
@@ -3739,7 +3740,8 @@ union bpf_attr {
  *		**sizeof**\ (**struct ip6hdr**).
  *
  *		*th* points to the start of the TCP header, while *th_len*
- *		contains the length of the TCP header.
+ *		contains the length of the TCP header (at least
+ *		**sizeof**\ (**struct tcphdr**)).
  *	Return
  *		On success, lower 32 bits hold the generated SYN cookie in
  *		followed by 16 bits which hold the MSS value for that cookie,
-- 
2.30.2