From f94fd25cb0aaf77fd7453f31c5d394a1a68ecf60 Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@kernel.dk>
Date: Thu, 28 Apr 2022 18:45:06 -0600
Subject: [PATCH] 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>
---
include/linux/socket.h | 6 +++++-
net/ipv4/tcp.c | 16 ++++++++++------
2 files changed, 15 insertions(+), 7 deletions(-)
diff --git a/include/linux/socket.h b/include/linux/socket.h
index 6f85f5d957efe..12085c9a85449 100644
--- a/include/linux/socket.h
+++ b/include/linux/socket.h
@@ -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 */
};
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index cf18fbcbf123a..bb7ef45408e1a 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -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;
--
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