freebsd-dev/sys/compat/linux/linux_socket.c

/*-
 * Copyright (c) 1995 S<EFBFBD>ren Schmidt
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer 
 *    in this position and unchanged.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software withough specific prior written permission
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * $FreeBSD$
 */

/* XXX we use functions that might not exist. */
#include "opt_compat.h"

#ifndef COMPAT_43
#error "Unable to compile Linux-emulator due to missing COMPAT_43 option!"
#endif

#include <sys/param.h>
#include <sys/proc.h>
#include <sys/systm.h>
#include <sys/sysproto.h>
#include <sys/fcntl.h>
#include <sys/socket.h>
#include <sys/uio.h>

#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>

#include <i386/linux/linux.h>
#include <i386/linux/linux_proto.h>
#include <i386/linux/linux_util.h>

static int
linux_to_bsd_domain(int domain)
{
    switch (domain) {
    case LINUX_AF_UNSPEC:
	return AF_UNSPEC;
    case LINUX_AF_UNIX:
	return AF_LOCAL;
    case LINUX_AF_INET:
	return AF_INET;
    case LINUX_AF_AX25:
	return AF_CCITT;
    case LINUX_AF_IPX:
	return AF_IPX;
    case LINUX_AF_APPLETALK:
	return AF_APPLETALK;
    default:
	return -1;
    }
}

static int
linux_to_bsd_sockopt_level(int level)
{
    switch (level) {
    case LINUX_SOL_SOCKET:
	return SOL_SOCKET;
    default:
	return level;
    }
}

static int linux_to_bsd_ip_sockopt(int opt)
{
    switch (opt) {
    case LINUX_IP_TOS:
	return IP_TOS;
    case LINUX_IP_TTL:
	return IP_TTL;
    case LINUX_IP_OPTIONS:
	return IP_OPTIONS;
    case LINUX_IP_MULTICAST_IF:
	return IP_MULTICAST_IF;
    case LINUX_IP_MULTICAST_TTL:
	return IP_MULTICAST_TTL;
    case LINUX_IP_MULTICAST_LOOP:
	return IP_MULTICAST_LOOP;
    case LINUX_IP_ADD_MEMBERSHIP:
	return IP_ADD_MEMBERSHIP;
    case LINUX_IP_DROP_MEMBERSHIP:
	return IP_DROP_MEMBERSHIP;
    case LINUX_IP_HDRINCL:
        return IP_HDRINCL;
    default:
	return -1;
    }
}

static int
linux_to_bsd_so_sockopt(int opt)
{
    switch (opt) {
    case LINUX_SO_DEBUG:
	return SO_DEBUG;
    case LINUX_SO_REUSEADDR:
	return SO_REUSEADDR;
    case LINUX_SO_TYPE:
	return SO_TYPE;
    case LINUX_SO_ERROR:
	return SO_ERROR;
    case LINUX_SO_DONTROUTE:
	return SO_DONTROUTE;
    case LINUX_SO_BROADCAST:
	return SO_BROADCAST;
    case LINUX_SO_SNDBUF:
	return SO_SNDBUF;
    case LINUX_SO_RCVBUF:
	return SO_RCVBUF;
    case LINUX_SO_KEEPALIVE:
	return SO_KEEPALIVE;
    case LINUX_SO_OOBINLINE:
	return SO_OOBINLINE;
    case LINUX_SO_LINGER:
	return SO_LINGER;
    case LINUX_SO_PRIORITY:
    case LINUX_SO_NO_CHECK:
    default:
	return -1;
    }
}

/* Return 0 if IP_HDRINCL is set of the given socket, not 0 otherwise */
static int
linux_check_hdrincl(struct proc *p, int s)
{
    struct getsockopt_args /* {
	int s;
	int level;
	int name;
	caddr_t val;
	int *avalsize;
    } */ bsd_args;
    int error;
    caddr_t sg, val, valsize;
    int size_val = sizeof val;
    int optval;

    sg = stackgap_init();
    val = stackgap_alloc(&sg, sizeof(int));
    valsize = stackgap_alloc(&sg, sizeof(int));

    if ((error=copyout(&size_val, valsize, sizeof(size_val))))
	return error;
    bsd_args.s = s;
    bsd_args.level = IPPROTO_IP;
    bsd_args.name = IP_HDRINCL;
    bsd_args.val = val;
    bsd_args.avalsize = (int *)valsize;
    if ((error=getsockopt(p, &bsd_args)))
	return error;
    if ((error=copyin(val, &optval, sizeof(optval))))
	return error;
    return optval == 0;
}

/*
 * Updated sendto() when IP_HDRINCL is set:
 * tweak endian-dependent fields in the IP packet.
 */
static int
linux_sendto_hdrincl(struct proc *p, struct sendto_args *bsd_args)
{
/*
 * linux_ip_copysize defines how many bytes we should copy
 * from the beginning of the IP packet before we customize it for BSD.
 * It should include all the fields we modify (ip_len and ip_off)
 * and be as small as possible to minimize copying overhead.
 */
#define linux_ip_copysize	8

    caddr_t sg;
    struct ip *packet;
    struct msghdr *msg;
    struct iovec *iov;

    int error;
    struct  sendmsg_args /* {
	int s;
	caddr_t msg;
	int flags;
    } */ sendmsg_args;

    /* Check the packet isn't too small before we mess with it */
    if (bsd_args->len < linux_ip_copysize)
	return EINVAL;

    /*
     * Tweaking the user buffer in place would be bad manners.
     * We create a corrected IP header with just the needed length,
     * then use an iovec to glue it to the rest of the user packet
     * when calling sendmsg().
     */
    sg = stackgap_init();
    packet = (struct ip *)stackgap_alloc(&sg, linux_ip_copysize);
    msg = (struct msghdr *)stackgap_alloc(&sg, sizeof(*msg));
    iov = (struct iovec *)stackgap_alloc(&sg, sizeof(*iov)*2);

    /* Make a copy of the beginning of the packet to be sent */
    if ((error = copyin(bsd_args->buf, (caddr_t)packet, linux_ip_copysize)))
	return error;

    /* Convert fields from Linux to BSD raw IP socket format */
    packet->ip_len = bsd_args->len;
    packet->ip_off = ntohs(packet->ip_off);

    /* Prepare the msghdr and iovec structures describing the new packet */
    msg->msg_name = bsd_args->to;
    msg->msg_namelen = bsd_args->tolen;
    msg->msg_iov = iov;
    msg->msg_iovlen = 2;
    msg->msg_control = NULL;
    msg->msg_controllen = 0;
    msg->msg_flags = 0;
    iov[0].iov_base = (char *)packet;
    iov[0].iov_len = linux_ip_copysize;
    iov[1].iov_base = (char *)(bsd_args->buf) + linux_ip_copysize;
    iov[1].iov_len = bsd_args->len - linux_ip_copysize;

    sendmsg_args.s = bsd_args->s;
    sendmsg_args.msg = (caddr_t)msg;
    sendmsg_args.flags = bsd_args->flags;
    return sendmsg(p, &sendmsg_args);
}

struct linux_socket_args {
    int domain;
    int type;
    int protocol;
};

static int
linux_socket(struct proc *p, struct linux_socket_args *args)
{
    struct linux_socket_args linux_args;
    struct socket_args /* {
	int domain;
	int type;
	int protocol;
    } */ bsd_args;
    int error;
    int retval_socket;

    if ((error=copyin((caddr_t)args, (caddr_t)&linux_args, sizeof(linux_args))))
	return error;
    bsd_args.protocol = linux_args.protocol;
    bsd_args.type = linux_args.type;
    bsd_args.domain = linux_to_bsd_domain(linux_args.domain);
    if (bsd_args.domain == -1)
	return EINVAL;

    retval_socket = socket(p, &bsd_args);
    if (bsd_args.type == SOCK_RAW
	&& (bsd_args.protocol == IPPROTO_RAW || bsd_args.protocol == 0)
	&& bsd_args.domain == AF_INET
	&& retval_socket >= 0) {
	/* It's a raw IP socket: set the IP_HDRINCL option. */
	struct setsockopt_args /* {
	    int s;
	    int level;
	    int name;
	    caddr_t val;
	    int valsize;
	} */ bsd_setsockopt_args;
	caddr_t sg;
	int *hdrincl;

	sg = stackgap_init();
	hdrincl = (int *)stackgap_alloc(&sg, sizeof(*hdrincl));
	*hdrincl = 1;
	bsd_setsockopt_args.s = p->p_retval[0];
	bsd_setsockopt_args.level = IPPROTO_IP;
	bsd_setsockopt_args.name = IP_HDRINCL;
	bsd_setsockopt_args.val = (caddr_t)hdrincl;
	bsd_setsockopt_args.valsize = sizeof(*hdrincl);
	/* We ignore any error returned by setsockopt() */
	setsockopt(p, &bsd_setsockopt_args);
	/* Copy back the return value from socket() */
	p->p_retval[0] = bsd_setsockopt_args.s;
    }
    return retval_socket;
}

struct linux_bind_args {
    int s;
    struct sockaddr *name;
    int namelen;
};

static int
linux_bind(struct proc *p, struct linux_bind_args *args)
{
    struct linux_bind_args linux_args;
    struct bind_args /* {
	int s;
	caddr_t name;
	int namelen;
    } */ bsd_args;
    int error;

    if ((error=copyin((caddr_t)args, (caddr_t)&linux_args, sizeof(linux_args))))
	return error;
    bsd_args.s = linux_args.s;
    bsd_args.name = (caddr_t)linux_args.name;
    bsd_args.namelen = linux_args.namelen;
    return bind(p, &bsd_args);
}

struct linux_connect_args {
    int s;
    struct sockaddr * name;
    int namelen;
};

static int
linux_connect(struct proc *p, struct linux_connect_args *args)
{
    struct linux_connect_args linux_args;
    struct connect_args /* {
	int s;
	caddr_t name;
	int namelen;
    } */ bsd_args;
    int error;

    if ((error=copyin((caddr_t)args, (caddr_t)&linux_args, sizeof(linux_args))))
	return error;
    bsd_args.s = linux_args.s;
    bsd_args.name = (caddr_t)linux_args.name;
    bsd_args.namelen = linux_args.namelen;
    error = connect(p, &bsd_args);
    if (error == EISCONN) {
	/*
	 * Linux doesn't return EISCONN the first time it occurs,
	 * when on a non-blocking socket. Instead it returns the
	 * error getsockopt(SOL_SOCKET, SO_ERROR) would return on BSD.
	 */
	struct fcntl_args /* {
	    int fd;
	    int cmd;
	    int arg;
	} */ bsd_fcntl_args;
	struct getsockopt_args /* {
	    int s;
	    int level;
	    int name;
	    caddr_t val;
	    int *avalsize;
	} */ bsd_getsockopt_args;
	void *status, *statusl;
	int stat, statl = sizeof stat;
	caddr_t sg;

	/* Check for non-blocking */
	bsd_fcntl_args.fd = linux_args.s;
	bsd_fcntl_args.cmd = F_GETFL;
	bsd_fcntl_args.arg = 0;
	error = fcntl(p, &bsd_fcntl_args);
	if (error == 0 && (p->p_retval[0] & O_NONBLOCK)) {
	    sg = stackgap_init();
	    status = stackgap_alloc(&sg, sizeof stat);
	    statusl = stackgap_alloc(&sg, sizeof statusl);

	    if ((error = copyout(&statl, statusl, sizeof statl)))
		return error;

	    bsd_getsockopt_args.s = linux_args.s;
	    bsd_getsockopt_args.level = SOL_SOCKET;
	    bsd_getsockopt_args.name = SO_ERROR;
	    bsd_getsockopt_args.val = status;
	    bsd_getsockopt_args.avalsize = statusl;

	    error = getsockopt(p, &bsd_getsockopt_args);
	    if (error)
		return error;
	    if ((error = copyin(status, &stat, sizeof stat)))
		return error;  
	    p->p_retval[0] = stat;
	    return 0;
	}
    }
    return error;
}

struct linux_listen_args {
    int s;
    int backlog;
};

static int
linux_listen(struct proc *p, struct linux_listen_args *args)
{
    struct linux_listen_args linux_args;
    struct listen_args /* {
	int s;
	int backlog;
    } */ bsd_args;
    int error;

    if ((error=copyin((caddr_t)args, (caddr_t)&linux_args, sizeof(linux_args))))
	return error;
    bsd_args.s = linux_args.s;
    bsd_args.backlog = linux_args.backlog;
    return listen(p, &bsd_args);
}

struct linux_accept_args {
    int s;
    struct sockaddr *addr;
    int *namelen;
};

static int
linux_accept(struct proc *p, struct linux_accept_args *args)
{
    struct linux_accept_args linux_args;
    struct accept_args /* {
	int s;
	caddr_t name;
	int *anamelen;
    } */ bsd_args;
    int error;

    if ((error=copyin((caddr_t)args, (caddr_t)&linux_args, sizeof(linux_args))))
	return error;
    bsd_args.s = linux_args.s;
    bsd_args.name = (caddr_t)linux_args.addr;
    bsd_args.anamelen = linux_args.namelen;
    return oaccept(p, &bsd_args);
}

struct linux_getsockname_args {
    int s;
    struct sockaddr *addr;
    int *namelen;
};

static int
linux_getsockname(struct proc *p, struct linux_getsockname_args *args)
{
    struct linux_getsockname_args linux_args;
    struct getsockname_args /* {
	int fdes;
	caddr_t asa;
	int *alen;
    } */ bsd_args;
    int error;

    if ((error=copyin((caddr_t)args, (caddr_t)&linux_args, sizeof(linux_args))))
	return error;
    bsd_args.fdes = linux_args.s;
    bsd_args.asa = (caddr_t) linux_args.addr;
    bsd_args.alen = linux_args.namelen;
    return ogetsockname(p, &bsd_args);
}

struct linux_getpeername_args {
    int s;
    struct sockaddr *addr;
    int *namelen;
};

static int
linux_getpeername(struct proc *p, struct linux_getpeername_args *args)
{
    struct linux_getpeername_args linux_args;
    struct ogetpeername_args /* {
	int fdes;
	caddr_t asa;
	int *alen;
    } */ bsd_args;
    int error;

    if ((error=copyin((caddr_t)args, (caddr_t)&linux_args, sizeof(linux_args))))
	return error;
    bsd_args.fdes = linux_args.s;
    bsd_args.asa = (caddr_t) linux_args.addr;
    bsd_args.alen = linux_args.namelen;
    return ogetpeername(p, &bsd_args);
}

struct linux_socketpair_args {
    int domain;
    int type;
    int protocol;
    int *rsv;
};

static int
linux_socketpair(struct proc *p, struct linux_socketpair_args *args)
{
    struct linux_socketpair_args linux_args;
    struct socketpair_args /* {
	int domain;
	int type;
	int protocol;
	int *rsv;
    } */ bsd_args;
    int error;

    if ((error=copyin((caddr_t)args, (caddr_t)&linux_args, sizeof(linux_args))))
	return error;
    bsd_args.domain = linux_to_bsd_domain(linux_args.domain);
    if (bsd_args.domain == -1)
	return EINVAL;
    bsd_args.type = linux_args.type;
    bsd_args.protocol = linux_args.protocol;
    bsd_args.rsv = linux_args.rsv;
    return socketpair(p, &bsd_args);
}

struct linux_send_args {
    int s;
    void *msg;
    int len;
    int flags;
};

static int
linux_send(struct proc *p, struct linux_send_args *args)
{
    struct linux_send_args linux_args;
    struct osend_args /* {
	int s;
	caddr_t buf;
	int len;
	int flags;
    } */ bsd_args;
    int error;

    if ((error=copyin((caddr_t)args, (caddr_t)&linux_args, sizeof(linux_args))))
	return error;
    bsd_args.s = linux_args.s;
    bsd_args.buf = linux_args.msg;
    bsd_args.len = linux_args.len;
    bsd_args.flags = linux_args.flags;
    return osend(p, &bsd_args);
}

struct linux_recv_args {
    int s;
    void *msg;
    int len;
    int flags;
};

static int
linux_recv(struct proc *p, struct linux_recv_args *args)
{
    struct linux_recv_args linux_args;
    struct orecv_args /* {
	int s;
	caddr_t buf;
	int len;
	int flags;
    } */ bsd_args;
    int error;

    if ((error=copyin((caddr_t)args, (caddr_t)&linux_args, sizeof(linux_args))))
	return error;
    bsd_args.s = linux_args.s;
    bsd_args.buf = linux_args.msg;
    bsd_args.len = linux_args.len;
    bsd_args.flags = linux_args.flags;
    return orecv(p, &bsd_args);
}

struct linux_sendto_args {
    int s;
    void *msg;
    int len;
    int flags;
    caddr_t to;
    int tolen;
};

static int
linux_sendto(struct proc *p, struct linux_sendto_args *args)
{
    struct linux_sendto_args linux_args;
    struct sendto_args /* {
	int s;
	caddr_t buf;
	size_t len;
	int flags;
	caddr_t to;
	int tolen;
    } */ bsd_args;
    int error;

    if ((error=copyin((caddr_t)args, (caddr_t)&linux_args, sizeof(linux_args))))
	return error;
    bsd_args.s = linux_args.s;
    bsd_args.buf = linux_args.msg;
    bsd_args.len = linux_args.len;
    bsd_args.flags = linux_args.flags;
    bsd_args.to = linux_args.to;
    bsd_args.tolen = linux_args.tolen;

    if (linux_check_hdrincl(p, linux_args.s) == 0)
	/* IP_HDRINCL set, tweak the packet before sending */
	return linux_sendto_hdrincl(p, &bsd_args);

    return sendto(p, &bsd_args);
}

struct linux_recvfrom_args {
    int s;
    void *buf;
    int len;
    int flags;
    caddr_t from;
    int *fromlen;
};

static int
linux_recvfrom(struct proc *p, struct linux_recvfrom_args *args)
{
    struct linux_recvfrom_args linux_args;
    struct recvfrom_args /* {
	int s;
	caddr_t buf;
	size_t len;
	int flags;
	caddr_t from;
	int *fromlenaddr;
    } */ bsd_args;
    int error;

    if ((error=copyin((caddr_t)args, (caddr_t)&linux_args, sizeof(linux_args))))
	return error;
    bsd_args.s = linux_args.s;
    bsd_args.buf = linux_args.buf;
    bsd_args.len = linux_args.len;
    bsd_args.flags = linux_args.flags;
    bsd_args.from = linux_args.from;
    bsd_args.fromlenaddr = linux_args.fromlen;
    return orecvfrom(p, &bsd_args);
}

struct linux_shutdown_args {
    int s;
    int how;
};

static int
linux_shutdown(struct proc *p, struct linux_shutdown_args *args)
{
    struct linux_shutdown_args linux_args;
    struct shutdown_args /* {
	int s;
	int how;
    } */ bsd_args;
    int error;

    if ((error=copyin((caddr_t)args, (caddr_t)&linux_args, sizeof(linux_args))))
	return error;
    bsd_args.s = linux_args.s;
    bsd_args.how = linux_args.how;
    return shutdown(p, &bsd_args);
}

struct linux_setsockopt_args {
    int s;
    int level;
    int optname;
    void *optval;
    int optlen;
};

static int
linux_setsockopt(struct proc *p, struct linux_setsockopt_args *args)
{
    struct linux_setsockopt_args linux_args;
    struct setsockopt_args /* {
	int s;
	int level;
	int name;
	caddr_t val;
	int valsize;
    } */ bsd_args;
    int error, name;

    if ((error=copyin((caddr_t)args, (caddr_t)&linux_args, sizeof(linux_args))))
	return error;
    bsd_args.s = linux_args.s;
    bsd_args.level = linux_to_bsd_sockopt_level(linux_args.level);
    switch (bsd_args.level) {
    case SOL_SOCKET:
	name = linux_to_bsd_so_sockopt(linux_args.optname);
	break;
    case IPPROTO_IP:
	name = linux_to_bsd_ip_sockopt(linux_args.optname);
	break;
    case IPPROTO_TCP:
	/* Linux TCP option values match BSD's */
	name = linux_args.optname;
	break;
    default:
	return EINVAL;
    }
    if (name == -1)
	return EINVAL;
    bsd_args.name = name;
    bsd_args.val = linux_args.optval;
    bsd_args.valsize = linux_args.optlen;
    return setsockopt(p, &bsd_args);
}

struct linux_getsockopt_args {
    int s;
    int level;
    int optname;
    void *optval;
    int *optlen;
};

static int
linux_getsockopt(struct proc *p, struct linux_getsockopt_args *args)
{
    struct linux_getsockopt_args linux_args;
    struct getsockopt_args /* {
	int s;
	int level;
	int name;
	caddr_t val;
	int *avalsize;
    } */ bsd_args;
    int error, name;

    if ((error=copyin((caddr_t)args, (caddr_t)&linux_args, sizeof(linux_args))))
	return error;
    bsd_args.s = linux_args.s;
    bsd_args.level = linux_to_bsd_sockopt_level(linux_args.level);
    switch (bsd_args.level) {
    case SOL_SOCKET:
	name = linux_to_bsd_so_sockopt(linux_args.optname);
	break;
    case IPPROTO_IP:
	name = linux_to_bsd_ip_sockopt(linux_args.optname);
	break;
    case IPPROTO_TCP:
	/* Linux TCP option values match BSD's */
	name = linux_args.optname;
	break;
    default:
	return EINVAL;
    }
    if (name == -1)
	return EINVAL;
    bsd_args.name = name;
    bsd_args.val = linux_args.optval;
    bsd_args.avalsize = linux_args.optlen;
    return getsockopt(p, &bsd_args);
}

int
linux_socketcall(struct proc *p, struct linux_socketcall_args *args)
{
    switch (args->what) {
    case LINUX_SOCKET:
	return linux_socket(p, args->args);
    case LINUX_BIND:
	return linux_bind(p, args->args);
    case LINUX_CONNECT:
	return linux_connect(p, args->args);
    case LINUX_LISTEN:
	return linux_listen(p, args->args);
    case LINUX_ACCEPT:
	return linux_accept(p, args->args);
    case LINUX_GETSOCKNAME:
	return linux_getsockname(p, args->args);
    case LINUX_GETPEERNAME:
	return linux_getpeername(p, args->args);
    case LINUX_SOCKETPAIR:
	return linux_socketpair(p, args->args);
    case LINUX_SEND:
	return linux_send(p, args->args);
    case LINUX_RECV:
	return linux_recv(p, args->args);
    case LINUX_SENDTO:
	return linux_sendto(p, args->args);
    case LINUX_RECVFROM:
	return linux_recvfrom(p, args->args);
    case LINUX_SHUTDOWN:
	return linux_shutdown(p, args->args);
    case LINUX_SETSOCKOPT:
	return linux_setsockopt(p, args->args);
    case LINUX_GETSOCKOPT:
	return linux_getsockopt(p, args->args);
    case LINUX_SENDMSG:
	do {
		int error;
		int level;
		caddr_t control;
		struct {
			int s;
			const struct msghdr *msg;
			int flags;
		} *uap = args->args;

		error = copyin(&uap->msg->msg_control,
				&control, sizeof(caddr_t));
		if (error)
			return error;
		if (control == NULL)
			goto done;
		error = copyin(&((struct cmsghdr *)control)->cmsg_level,
				&level, sizeof(int));
		if (error)
			return error;
		if (level == 1) {
		/*
		 * Linux thinks that SOL_SOCKET is 1; we know that it's really
		 * 0xffff, of course.
		 */
			level = SOL_SOCKET;
			error = copyout(&level, &((struct cmsghdr *)control)->
					cmsg_level, sizeof(int));
			if (error)
				return error;
		}
	done:
		return sendmsg(p, args->args);
	} while (0);
    case LINUX_RECVMSG:
	return recvmsg(p, args->args);

    default:
	uprintf("LINUX: 'socket' typ=%d not implemented\n", args->what);
	return ENOSYS;
    }
}