From 2a100317c9ebc204a166f16294884fbf9da074ce Mon Sep 17 00:00:00 2001 From: John Fastabend Date: Sun, 18 Mar 2018 12:57:15 -0700 Subject: bpf: sockmap, add bpf_msg_apply_bytes() helper A single sendmsg or sendfile system call can contain multiple logical messages that a BPF program may want to read and apply a verdict. But, without an apply_bytes helper any verdict on the data applies to all bytes in the sendmsg/sendfile. Alternatively, a BPF program may only care to read the first N bytes of a msg. If the payload is large say MB or even GB setting up and calling the BPF program repeatedly for all bytes, even though the verdict is already known, creates unnecessary overhead. To allow BPF programs to control how many bytes a given verdict applies to we implement a bpf_msg_apply_bytes() helper. When called from within a BPF program this sets a counter, internal to the BPF infrastructure, that applies the last verdict to the next N bytes. If the N is smaller than the current data being processed from a sendmsg/sendfile call, the first N bytes will be sent and the BPF program will be re-run with start_data pointing to the N+1 byte. If N is larger than the current data being processed the BPF verdict will be applied to multiple sendmsg/sendfile calls until N bytes are consumed. Note1 if a socket closes with apply_bytes counter non-zero this is not a problem because data is not being buffered for N bytes and is sent as its received. Signed-off-by: John Fastabend Acked-by: David S. Miller Acked-by: Alexei Starovoitov Signed-off-by: Daniel Borkmann --- include/uapi/linux/bpf.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'include/uapi/linux/bpf.h') diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index ef529539abde..a557a2a5d72d 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -791,7 +791,8 @@ union bpf_attr { FN(getsockopt), \ FN(override_return), \ FN(sock_ops_cb_flags_set), \ - FN(msg_redirect_map), + FN(msg_redirect_map), \ + FN(msg_apply_bytes), /* integer value in 'imm' field of BPF_CALL instruction selects which helper * function eBPF program intends to call -- cgit v1.2.3-55-g7522