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Message-ID: References: <20260508073355.3916746-1-kuniyu@google.com> <20260508073355.3916746-4-kuniyu@google.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20260508073355.3916746-4-kuniyu@google.com> On 05/08, Kuniyuki Iwashima wrote: > When a TCP skb is queued to sk->sk_receive_queue, BPF SOCK_OPS > prog can be called with BPF_SOCK_OPS_RCVLOWAT_CB. > > In this hook, we want to parse the RPC descriptor in the skb > and adjust sk->sk_rcvlowat based on the RPC frame size. > > However, we cannot access payload via bpf_sock_ops.data on > modern NICs with TCP header/data split on as the payload is > not placed in the linear area. > > Let's support bpf_skb_load_bytes() for BPF_SOCK_OPS_RCVLOWAT_CB. > > Two notes: > > 1) bpf_sock_ops_kern.skb will be NULL when the BPF prog is > invoked from recvmsg(). > > 2) Access to bpf_sock_ops.data will be disabled by passing > 0 end_offset to bpf_skops_init_skb(). > > Signed-off-by: Kuniyuki Iwashima > --- > net/core/filter.c | 34 ++++++++++++++++++++++++++++++++++ > 1 file changed, 34 insertions(+) > > diff --git a/net/core/filter.c b/net/core/filter.c > index 5fa9189eb772..94d07a15b2ab 100644 > --- a/net/core/filter.c > +++ b/net/core/filter.c > @@ -7718,6 +7718,38 @@ static const struct bpf_func_proto bpf_sk_assign_proto = { > .arg3_type = ARG_ANYTHING, > }; > > +BPF_CALL_4(bpf_sock_ops_skb_load_bytes, struct bpf_sock_ops_kern *, bpf_sock, > + u32, offset, void *, to, u32, len) > +{ > + int err; > + > + if (bpf_sock->op != BPF_SOCK_OPS_RCVLOWAT_CB) { > + err = -EOPNOTSUPP; > + goto err_clear; > + } > + > + if (!bpf_sock->skb) { > + err = -EPERM; > + goto err_clear; > + } > + > + return ____bpf_skb_load_bytes(bpf_sock->skb, offset, to, len); nit: wondering whether it's better to use __bpf_skb_load_bytes (which wraps BPF_CALL_4's ____bpf_skb_load_bytes) here? Seems a bit less magic and used already by dynptr?