# \[PATCH bpf-next 05/10\] bpf: Fix documentation of th\_len in bpf\_tcp\_{gen,check}\_syncookie - From: Maxim Mikityanskiy \ - Date: 2021-10-19 14:48:19 - List: netdev - Page: https://ratatoskr.run/netdev/2021/10/7782607 - Thread: https://ratatoskr.run/netdev/2021/10/7782602/t.md ```text 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). Signed-off-by: Maxim Mikityanskiy Reviewed-by: Tariq Toukan --- 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 2f12b11f1259..efb2750f39c6 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -3543,7 +3543,8 @@ 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. * @@ -3743,7 +3744,8 @@ 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 2f12b11f1259..efb2750f39c6 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -3543,7 +3543,8 @@ 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. * @@ -3743,7 +3744,8 @@ 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 ```