On Tue, May 3, 2022 at 10:15 AM Maxim Mikityanskiy <maximmi@xxxxxxxxxx> wrote:
>
> The new helpers bpf_tcp_raw_{gen,check}_syncookie_ipv{4,6} allow an XDP
> program to generate SYN cookies in response to TCP SYN packets and to
> check those cookies upon receiving the first ACK packet (the final
> packet of the TCP handshake).
>
> Unlike bpf_tcp_{gen,check}_syncookie these new helpers don't need a
> listening socket on the local machine, which allows to use them together
> with synproxy to accelerate SYN cookie generation.
>
> Signed-off-by: Maxim Mikityanskiy <maximmi@xxxxxxxxxx>
> Reviewed-by: Tariq Toukan <tariqt@xxxxxxxxxx>
> ---
> include/net/tcp.h | 1 +
> include/uapi/linux/bpf.h | 78 ++++++++++++++++++++++
> net/core/filter.c | 118 +++++++++++++++++++++++++++++++++
> net/ipv4/tcp_input.c | 3 +-
> scripts/bpf_doc.py | 4 ++
> tools/include/uapi/linux/bpf.h | 78 ++++++++++++++++++++++
> 6 files changed, 281 insertions(+), 1 deletion(-)
>
> diff --git a/include/net/tcp.h b/include/net/tcp.h
> index 94a52ad1101c..45aafc28ce00 100644
> --- a/include/net/tcp.h
> +++ b/include/net/tcp.h
> @@ -432,6 +432,7 @@ u16 tcp_v4_get_syncookie(struct sock *sk, struct iphdr *iph,
> struct tcphdr *th, u32 *cookie);
> u16 tcp_v6_get_syncookie(struct sock *sk, struct ipv6hdr *iph,
> struct tcphdr *th, u32 *cookie);
> +u16 tcp_parse_mss_option(const struct tcphdr *th, u16 user_mss);
> u16 tcp_get_syncookie_mss(struct request_sock_ops *rsk_ops,
> const struct tcp_request_sock_ops *af_ops,
> struct sock *sk, struct tcphdr *th);
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 4dd9e34f2a60..5e611d898302 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -5156,6 +5156,80 @@ union bpf_attr {
> * if not NULL, is a reference which must be released using its
> * corresponding release function, or moved into a BPF map before
> * program exit.
> + *
> + * s64 bpf_tcp_raw_gen_syncookie_ipv4(struct iphdr *iph, struct tcphdr *th, u32 th_len)
> + * Description
> + * Try to issue a SYN cookie for the packet with corresponding
> + * IPv4/TCP headers, *iph* and *th*, without depending on a
> + * listening socket.
> + *
> + * *iph* points to the IPv4 header.
> + *
> + * *th* points to the start of the TCP header, while *th_len*
> + * 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,
> + * and the top 16 bits are unused.
> + *
> + * On failure, the returned value is one of the following:
> + *
> + * **-EINVAL** if *th_len* is invalid.
> + *
> + * s64 bpf_tcp_raw_gen_syncookie_ipv6(struct ipv6hdr *iph, struct tcphdr *th, u32 th_len)
> + * Description
> + * Try to issue a SYN cookie for the packet with corresponding
> + * IPv6/TCP headers, *iph* and *th*, without depending on a
> + * listening socket.
> + *
> + * *iph* points to the IPv6 header.
> + *
> + * *th* points to the start of the TCP header, while *th_len*
> + * 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,
> + * and the top 16 bits are unused.
> + *
> + * On failure, the returned value is one of the following:
> + *
> + * **-EINVAL** if *th_len* is invalid.
> + *
> + * **-EPROTONOSUPPORT** if CONFIG_IPV6 is not builtin.
> + *
> + * int bpf_tcp_raw_check_syncookie_ipv4(struct iphdr *iph, struct tcphdr *th)
Note that all existing helpers that just return error or 0 on success
return long. Please use long for consistency.
> + * Description
> + * Check whether *iph* and *th* contain a valid SYN cookie ACK
> + * without depending on a listening socket.
> + *
> + * *iph* points to the IPv4 header.
> + *
> + * *th* points to the TCP header.
> + * Return
> + * 0 if *iph* and *th* are a valid SYN cookie ACK.
> + *
> + * On failure, the returned value is one of the following:
> + *
> + * **-EACCES** if the SYN cookie is not valid.
> + *
> + * int bpf_tcp_raw_check_syncookie_ipv6(struct ipv6hdr *iph, struct tcphdr *th)
same
> + * Description
> + * Check whether *iph* and *th* contain a valid SYN cookie ACK
> + * without depending on a listening socket.
> + *
> + * *iph* points to the IPv6 header.
> + *
> + * *th* points to the TCP header.
> + * Return
> + * 0 if *iph* and *th* are a valid SYN cookie ACK.
> + *
> + * On failure, the returned value is one of the following:
> + *
> + * **-EACCES** if the SYN cookie is not valid.
> + *
> + * **-EPROTONOSUPPORT** if CONFIG_IPV6 is not builtin.
[...]
