On Tue, Jan 23, 2018 at 11:58 PM, Lawrence Brakmo <bra...@fb.com> wrote:
> Adds support for calling sock_ops BPF program when there is a
> retransmission. Two arguments are used; one for the sequence number and
> other for the number of segments retransmitted. Does not include syn-ack
> retransmissions.
>
> New op: BPF_SOCK_OPS_RETRANS_CB.
>
> Signed-off-by: Lawrence Brakmo <bra...@fb.com>
> ---
> include/uapi/linux/bpf.h | 4 ++++
> include/uapi/linux/tcp.h | 3 ++-
> net/ipv4/tcp_output.c | 3 +++
> 3 files changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 6998032..eb26cdb 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -1039,6 +1039,10 @@ enum {
> * Arg2: value of icsk_rto
> * Arg3: whether RTO has expired
> */
> + BPF_SOCK_OPS_RETRANS_CB, /* Called when skb is retransmitted.
> + * Arg1: sequence number of 1st byte
> + * Arg2: # segments
> + */
> };
>
> #define TCP_BPF_IW 1001 /* Set TCP initial congestion window
> */
> diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h
> index 129032ca..ec03a2b 100644
> --- a/include/uapi/linux/tcp.h
> +++ b/include/uapi/linux/tcp.h
> @@ -270,7 +270,8 @@ struct tcp_diag_md5sig {
>
> /* Definitions for bpf_sock_ops_cb_flags */
> #define BPF_SOCK_OPS_RTO_CB_FLAG (1<<0)
> -#define BPF_SOCK_OPS_ALL_CB_FLAGS 0x1 /* Mask of all
> currently
> +#define BPF_SOCK_OPS_RETRANS_CB_FLAG (1<<1)
> +#define BPF_SOCK_OPS_ALL_CB_FLAGS 0x3 /* Mask of all
> currently
> * supported cb flags
> */
>
> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> index d12f7f7..f7d34f01 100644
> --- a/net/ipv4/tcp_output.c
> +++ b/net/ipv4/tcp_output.c
> @@ -2908,6 +2908,9 @@ int __tcp_retransmit_skb(struct sock *sk, struct
> sk_buff *skb, int segs)
> if (likely(!err)) {
> TCP_SKB_CB(skb)->sacked |= TCPCB_EVER_RETRANS;
> trace_tcp_retransmit_skb(sk, skb);
> + if (BPF_SOCK_OPS_TEST_FLAG(tp, BPF_SOCK_OPS_RETRANS_CB_FLAG))
> + tcp_call_bpf_2arg(sk, BPF_SOCK_OPS_RETRANS_CB,
> + TCP_SKB_CB(skb)->seq, segs);
Any reason to skip failed retransmission? I would think that's helpful as well.
> } else if (err != -EBUSY) {
> NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRETRANSFAIL);
> }
> --
> 2.9.5
>
