On Tue, May 10, 2022 at 12:20 PM Maxim Mikityanskiy <maximmi@xxxxxxxxxx> wrote:
>
> On 2022-05-07 00:19, Andrii Nakryiko wrote:
> > 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.
>
> OK. There are some existing helpers that return int, though:
> bpf_inode_storage_delete, bpf_get_retval, bpf_set_retval. They should
> probably be fixed by someone as well.
>
Yep, they probably should, thanks for pointing missed cases out!
> >> + * 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.
> >
> > [...]
>
