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tcp: pass back data left in socket after receive 

This is currently done for CMSG_INQ, add an ability to do so via struct
msghdr as well and have CMSG_INQ use that too. If the caller sets
msghdr->msg_get_inq, then we'll pass back the hint in msghdr->msg_inq.

Rearrange struct msghdr a bit so we can add this member while shrinking
it at the same time. On a 64-bit build, it was 96 bytes before this
change and 88 bytes afterwards.

Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Link: https://lore.kernel.org/r/650c22ca-cffc-0255-9a05-2413a1e20826@kernel.dk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Jens Axboe 2022-04-28 18:45:06 -06:00 committed by Jakub Kicinski
parent af2d861d4c
commit f94fd25cb0
2 changed files with 15 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
include/linux/socket.h
View File

@ -50,6 +50,9 @@ struct linger {
struct msghdr {
void *msg_name; /* ptr to socket address structure */
int msg_namelen; /* size of socket address structure */
int msg_inq; /* output, data left in socket */
struct iov_iter msg_iter; /* data */
/*
@ -62,8 +65,9 @@ struct msghdr {
void __user *msg_control_user;
};
bool msg_control_is_user : 1;
__kernel_size_t msg_controllen; /* ancillary data buffer length */
bool msg_get_inq : 1;/* return INQ after receive */
unsigned int msg_flags; /* flags on received message */
__kernel_size_t msg_controllen; /* ancillary data buffer length */
struct kiocb *msg_iocb; /* ptr to iocb for async requests */
};

16
net/ipv4/tcp.c
View File

@ -2335,8 +2335,10 @@ static int tcp_recvmsg_locked(struct sock *sk, struct msghdr *msg, size_t len,
if (sk->sk_state == TCP_LISTEN)
goto out;
if (tp->recvmsg_inq)
if (tp->recvmsg_inq) {
*cmsg_flags = TCP_CMSG_INQ;
msg->msg_get_inq = 1;
}
timeo = sock_rcvtimeo(sk, nonblock);
/* Urgent data needs to be handled specially. */
@ -2559,7 +2561,7 @@ recv_sndq:
int tcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int nonblock,
int flags, int *addr_len)
{
int cmsg_flags = 0, ret, inq;
int cmsg_flags = 0, ret;
struct scm_timestamping_internal tss;
if (unlikely(flags & MSG_ERRQUEUE))
@ -2576,12 +2578,14 @@ int tcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int nonblock,
release_sock(sk);
sk_defer_free_flush(sk);
if (cmsg_flags && ret >= 0) {
if ((cmsg_flags || msg->msg_get_inq) && ret >= 0) {
if (cmsg_flags & TCP_CMSG_TS)
tcp_recv_timestamp(msg, sk, &tss);
if (cmsg_flags & TCP_CMSG_INQ) {
inq = tcp_inq_hint(sk);
put_cmsg(msg, SOL_TCP, TCP_CM_INQ, sizeof(inq), &inq);
if (msg->msg_get_inq) {
msg->msg_inq = tcp_inq_hint(sk);
if (cmsg_flags & TCP_CMSG_INQ)
put_cmsg(msg, SOL_TCP, TCP_CM_INQ,
sizeof(msg->msg_inq), &msg->msg_inq);
}
}
return ret;