On 6/20/17, 2:25 PM, "Craig Gallek" <kraigatg...@gmail.com> wrote:
On Mon, Jun 19, 2017 at 11:00 PM, Lawrence Brakmo <bra...@fb.com> wrote:
> Added support for calling a subset of socket setsockopts from
> BPF_PROG_TYPE_SOCK_OPS programs. The code was duplicated rather
> than making the changes to call the socket setsockopt function because
> the changes required would have been larger.
>
> @@ -2671,6 +2672,69 @@ static const struct bpf_func_proto
bpf_get_socket_uid_proto = {
> .arg1_type = ARG_PTR_TO_CTX,
> };
>
> +BPF_CALL_5(bpf_setsockopt, struct bpf_sock_ops_kern *, bpf_sock,
> + int, level, int, optname, char *, optval, int, optlen)
> +{
> + struct sock *sk = bpf_sock->sk;
> + int ret = 0;
> + int val;
> +
> + if (bpf_sock->is_req_sock)
> + return -EINVAL;
> +
> + if (level == SOL_SOCKET) {
> + /* Only some socketops are supported */
> + val = *((int *)optval);
> +
> + switch (optname) {
> + case SO_RCVBUF:
> + sk->sk_userlocks |= SOCK_RCVBUF_LOCK;
> + sk->sk_rcvbuf = max_t(int, val * 2,
SOCK_MIN_RCVBUF);
> + break;
> + case SO_SNDBUF:
> + sk->sk_userlocks |= SOCK_SNDBUF_LOCK;
> + sk->sk_sndbuf = max_t(int, val * 2,
SOCK_MIN_SNDBUF);
> + break;
> + case SO_MAX_PACING_RATE:
> + sk->sk_max_pacing_rate = val;
> + sk->sk_pacing_rate = min(sk->sk_pacing_rate,
> + sk->sk_max_pacing_rate);
> + break;
> + case SO_PRIORITY:
> + sk->sk_priority = val;
> + break;
> + case SO_RCVLOWAT:
> + if (val < 0)
> + val = INT_MAX;
> + sk->sk_rcvlowat = val ? : 1;
> + break;
> + case SO_MARK:
> + sk->sk_mark = val;
> + break;
Isn't the socket lock required when manipulating these fields? It's
not obvious that the lock is held from every bpf hook point that could
trigger this function...
The sock_ops BPF programs are being called from within the network
stack and my understanding is that lock has already been taken.
Currently they are only called:
(1) after a packet is received, where there is the call to
bh_lock_sock_nested() in tcp_v4_rcv() before calling
tcp_v4_do_rcv().
(2) in tcp_connect(), where there should be no issue
Just in case I added a check “sock_owned_by_me(sk)” in tcp_call_bpf()
Do you think this is enough, or should I explicitly add a bh_lock_sock_nested
in the bpf_setsockopt function?
