Commit f94fd25c authored by Jens Axboe's avatar Jens Axboe Committed by Jakub Kicinski
Browse files

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: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
Link: https://lore.kernel.org/r/650c22ca-cffc-0255-9a05-2413a1e20826@kernel.dk


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent af2d861d

include/linux/socket.h

+5 −1
Original line number Diff line number Diff line
@@ -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 */

};

net/ipv4/tcp.c

+10 −6
Original line number Diff line number Diff line
@@ -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 @@ static int tcp_recvmsg_locked(struct sock *sk, struct msghdr *msg, size_t len, 
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;