From: Eric Dumazet <edumazet@google.com>
To: Martin KaFai Lau <kafai@fb.com>
Cc: bpf <bpf@vger.kernel.org>, Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
kernel-team <kernel-team@fb.com>, Lawrence Brakmo <brakmo@fb.com>,
Neal Cardwell <ncardwell@google.com>,
netdev <netdev@vger.kernel.org>,
Yuchung Cheng <ycheng@google.com>
Subject: Re: [PATCH v3 bpf-next 1/9] tcp: Use a struct to represent a saved_syn
Date: Fri, 31 Jul 2020 08:57:29 -0700 [thread overview]
Message-ID: <CANn89iK8h8x6oVZ0O0P+3gs1NyxfX0F--+Gw4CjOBhHE0NxqqA@mail.gmail.com> (raw)
In-Reply-To: <20200730205704.3352619-1-kafai@fb.com>
On Thu, Jul 30, 2020 at 1:57 PM Martin KaFai Lau <kafai@fb.com> wrote:
>
> The TCP_SAVE_SYN has both the network header and tcp header.
> The total length of the saved syn packet is currently stored in
> the first 4 bytes (u32) of an array and the actual packet data is
> stored after that.
>
> A latter patch will add a bpf helper that allows to get the tcp header
s/latter/later/
> alone from the saved syn without the network header. It will be more
> convenient to have a direct offset to a specific header instead of
> re-parsing it. This requires to separately store the network hdrlen.
> The total header length (i.e. network + tcp) is still needed for the
> current usage in getsockopt. Although this total length can be obtained
> by looking into the tcphdr and then get the (th->doff << 2), this patch
> chooses to directly store the tcp hdrlen in the second four bytes of
> this newly created "struct saved_syn". By using a new struct, it can
> give a readable name to each individual header length.
>
> Signed-off-by: Martin KaFai Lau <kafai@fb.com>
> diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
> index a018bafd7bdf..6c38ca9de17e 100644
> --- a/net/ipv4/tcp_input.c
> +++ b/net/ipv4/tcp_input.c
> @@ -6598,13 +6598,14 @@ static void tcp_reqsk_record_syn(const struct sock *sk,
> {
> if (tcp_sk(sk)->save_syn) {
> u32 len = skb_network_header_len(skb) + tcp_hdrlen(skb);
> - u32 *copy;
> -
> - copy = kmalloc(len + sizeof(u32), GFP_ATOMIC);
> - if (copy) {
> - copy[0] = len;
> - memcpy(©[1], skb_network_header(skb), len);
> - req->saved_syn = copy;
> + struct saved_syn *saved_syn;
> +
> + saved_syn = kmalloc(len + sizeof(*saved_syn), GFP_ATOMIC);
Please use
saved_syn = kmalloc(struct_size(saved_syn, data,
len), GFP_ATOMIC)
This will avoid yet another trivial patch in the future.
> + if (saved_syn) {
> + saved_syn->network_hdrlen = skb_network_header_len(skb);
> + saved_syn->tcp_hdrlen = tcp_hdrlen(skb);
> + memcpy(saved_syn->data, skb_network_header(skb), len);
> + req->saved_syn = saved_syn;
> }
> }
> }
> --
> 2.24.1
>
next prev parent reply other threads:[~2020-07-31 15:57 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-30 20:56 [PATCH v3 bpf-next 0/9] BPF TCP header options Martin KaFai Lau
2020-07-30 20:57 ` [PATCH v3 bpf-next 1/9] tcp: Use a struct to represent a saved_syn Martin KaFai Lau
2020-07-31 15:57 ` Eric Dumazet [this message]
2020-07-31 17:31 ` Eric Dumazet
2020-07-30 20:57 ` [PATCH v3 bpf-next 2/9] tcp: bpf: Add TCP_BPF_DELACK_MAX setsockopt Martin KaFai Lau
2020-07-30 20:57 ` [PATCH v3 bpf-next 3/9] tcp: bpf: Add TCP_BPF_RTO_MIN for bpf_setsockopt Martin KaFai Lau
2020-07-30 20:57 ` [PATCH v3 bpf-next 4/9] tcp: Add unknown_opt arg to tcp_parse_options Martin KaFai Lau
2020-07-31 16:12 ` Eric Dumazet
2020-07-31 17:37 ` Martin KaFai Lau
2020-07-30 20:57 ` [PATCH v3 bpf-next 5/9] bpf: sock_ops: Change some members of sock_ops_kern from u32 to u8 Martin KaFai Lau
2020-07-30 20:57 ` [PATCH v3 bpf-next 6/9] bpf: tcp: Allow bpf prog to write and parse TCP header option Martin KaFai Lau
2020-07-31 16:06 ` Eric Dumazet
2020-07-31 17:59 ` Martin KaFai Lau
2020-07-30 20:57 ` [PATCH v3 bpf-next 7/9] bpf: selftests: Add fastopen_connect to network_helpers Martin KaFai Lau
2020-07-30 20:57 ` [PATCH v3 bpf-next 8/9] bpf: selftests: tcp header options Martin KaFai Lau
2020-07-30 20:57 ` [PATCH v3 bpf-next 9/9] tcp: bpf: Optionally store mac header in TCP_SAVE_SYN Martin KaFai Lau
2020-07-31 15:51 ` Eric Dumazet
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