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unix: provide an option to return locked from unp_connectat()

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Use this new version in unix/dgram socket when sending to a target
address.  This removes extra lock release/acquisition and possible
counter-intuitive ENOTCONN.

Reviewed by:		markj
Differential revision:	https://reviews.freebsd.org/D35298
This commit is contained in:
Gleb Smirnoff 2022-06-24 09:09:10 -07:00
parent 5dc8dd5f3a
commit 315167c0de
1 changed files with 27 additions and 21 deletions
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48
sys/kern/uipc_usrreq.c
View File

@ -292,7 +292,7 @@ static int uipc_ctloutput(struct socket *, struct sockopt *);
static int unp_connect(struct socket *, struct sockaddr *,
struct thread *);
static int unp_connectat(int, struct socket *, struct sockaddr *,
struct thread *);
struct thread *, bool);
static void unp_connect2(struct socket *so, struct socket *so2, int);
static void unp_disconnect(struct unpcb *unp, struct unpcb *unp2);
static void unp_dispose(struct socket *so);
@ -721,7 +721,7 @@ uipc_connectat(int fd, struct socket *so, struct sockaddr *nam,
int error;
KASSERT(td == curthread, ("uipc_connectat: td != curthread"));
error = unp_connectat(fd, so, nam, td);
error = unp_connectat(fd, so, nam, td, false);
return (error);
}
@ -1212,22 +1212,20 @@ uipc_sosend_dgram(struct socket *so, struct sockaddr *addr, struct uio *uio,
}
SOCKBUF_UNLOCK(&so->so_snd);
if (addr != NULL && (error = unp_connect(so, addr, td)))
goto out3;
UNP_PCB_LOCK(unp);
/*
* Because connect() and send() are non-atomic in a sendto() with a
* target address, it's possible that the socket will have disconnected
* before the send() can run. In that case return the slightly
* counter-intuitive but otherwise correct error that the socket is not
* connected.
*/
unp2 = unp_pcb_lock_peer(unp);
if (unp2 == NULL) {
UNP_PCB_UNLOCK(unp);
error = ENOTCONN;
goto out3;
if (addr != NULL) {
if ((error = unp_connectat(AT_FDCWD, so, addr, td, true)))
goto out3;
UNP_PCB_LOCK_ASSERT(unp);
unp2 = unp->unp_conn;
UNP_PCB_LOCK_ASSERT(unp2);
} else {
UNP_PCB_LOCK(unp);
unp2 = unp_pcb_lock_peer(unp);
if (unp2 == NULL) {
UNP_PCB_UNLOCK(unp);
error = ENOTCONN;
goto out3;
}
}
if (unp2->unp_flags & UNP_WANTCRED_MASK)
@ -1828,12 +1826,12 @@ static int
unp_connect(struct socket *so, struct sockaddr *nam, struct thread *td)
{
return (unp_connectat(AT_FDCWD, so, nam, td));
return (unp_connectat(AT_FDCWD, so, nam, td, false));
}
static int
unp_connectat(int fd, struct socket *so, struct sockaddr *nam,
struct thread *td)
struct thread *td, bool return_locked)
{
struct mtx *vplock;
struct sockaddr_un *soun;
@ -1983,11 +1981,19 @@ unp_connectat(int fd, struct socket *so, struct sockaddr *nam,
KASSERT((unp->unp_flags & UNP_CONNECTING) != 0,
("%s: unp %p has UNP_CONNECTING clear", __func__, unp));
unp->unp_flags &= ~UNP_CONNECTING;
unp_pcb_unlock_pair(unp, unp2);
if (!return_locked)
unp_pcb_unlock_pair(unp, unp2);
bad2:
mtx_unlock(vplock);
bad:
if (vp != NULL) {
/*
* If we are returning locked (called via uipc_sosend_dgram()),
* we need to be sure that vput() won't sleep. This is
* guaranteed by VOP_UNP_CONNECT() call above and unp2 lock.
* SOCK_STREAM/SEQPACKET can't request return_locked (yet).
*/
MPASS(!(return_locked && connreq));
vput(vp);
}
free(sa, M_SONAME);