Function unp_connectat

freebsd/kern/uipc_usrreq.c:1498–1658

}

static int
unp_connectat(int fd, struct socket *so, struct sockaddr *nam,
    struct thread *td)
{
	struct mtx *vplock;
	struct sockaddr_un *soun;
	struct vnode *vp;
	struct socket *so2;
	struct unpcb *unp, *unp2, *unp3;
	struct nameidata nd;
	char buf[SOCK_MAXADDRLEN];
	struct sockaddr *sa;
	cap_rights_t rights;
	int error, len;
	bool connreq;

	if (nam->sa_family != AF_UNIX)
		return (EAFNOSUPPORT);
	if (nam->sa_len > sizeof(struct sockaddr_un))
		return (EINVAL);
	len = nam->sa_len - offsetof(struct sockaddr_un, sun_path);
	if (len <= 0)
		return (EINVAL);
	soun = (struct sockaddr_un *)nam;
	bcopy(soun->sun_path, buf, len);
	buf[len] = 0;

	unp = sotounpcb(so);
	UNP_PCB_LOCK(unp);
	for (;;) {
		/*
		 * Wait for connection state to stabilize.  If a connection
		 * already exists, give up.  For datagram sockets, which permit
		 * multiple consecutive connect(2) calls, upper layers are
		 * responsible for disconnecting in advance of a subsequent
		 * connect(2), but this is not synchronized with PCB connection
		 * state.
		 *
		 * Also make sure that no threads are currently attempting to
		 * lock the peer socket, to ensure that unp_conn cannot
		 * transition between two valid sockets while locks are dropped.
		 */
		if (unp->unp_conn != NULL) {
			UNP_PCB_UNLOCK(unp);
			return (EISCONN);
		}
		if ((unp->unp_flags & UNP_CONNECTING) != 0) {
			UNP_PCB_UNLOCK(unp);
			return (EALREADY);
		}
		if (unp->unp_pairbusy > 0) {
			unp->unp_flags |= UNP_WAITING;
			mtx_sleep(unp, UNP_PCB_LOCKPTR(unp), 0, "unpeer", 0);
			continue;
		}
		break;
	}
	unp->unp_flags |= UNP_CONNECTING;