libvirt_proxy.c

/*
 * proxy_svr.c: root suid proxy server for Xen access to APIs with no
 *              side effects from unauthenticated clients.
 *
 * Copyright (C) 2006 Red Hat, Inc.
 *
 * See COPYING.LIB for the License of this software
 *
 * Daniel Veillard <veillard@redhat.com>
 */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/poll.h>
#include <sys/socket.h>
#include <sys/un.h>
#include "proxy.h"
#include "internal.h"
#include "xen_internal.h"
#include "xend_internal.h"

static int fdServer = -1;
static int debug = 0;
static int persist = 0;
static int done = 0;

#define MAX_CLIENT 64

static int nbClients = 0; /* client 0 is the unix listen socket */
static struct pollfd pollInfos[MAX_CLIENT + 1];

static virConnect conninfos;
static virConnectPtr conn = &conninfos;

static unsigned long xenVersion = 0;

/************************************************************************
 *									*
 *	Interfaces with the Xen hypervisor				*
 *									*
 ************************************************************************/

/**
 * proxyInitXen:
 *
 * Initialize the communication layer with Xen
 *
 * Returns 0 or -1 in case of error
 */
static int
proxyInitXen(void) {
    int ret;
    unsigned long xenVersion2;

    ret = xenHypervisorOpen(conn, NULL, VIR_DRV_OPEN_QUIET);
    if (ret < 0) {
        fprintf(stderr, "Failed to open Xen hypervisor\n");
        return(-1);
    } else {
        ret = xenHypervisorGetVersion(conn, &xenVersion);
	if (ret != 0) {
	    fprintf(stderr, "Failed to get Xen hypervisor version\n");
	    return(-1);
	}
    }
    ret = xenDaemonOpen_unix(conn, "/var/lib/xend/xend-socket");
    if (ret < 0) {
        fprintf(stderr, "Failed to connect to Xen daemon\n");
        return(-1);
    }
    ret = xenDaemonGetVersion(conn, &xenVersion2);
    if (ret != 0) {
	fprintf(stderr, "Failed to get Xen daemon version\n");
	return(-1);
    }
    if (debug)
        fprintf(stderr, "Connected to hypervisor %lu and daemon %lu\n",
	        xenVersion, xenVersion2);
    if (xenVersion2 > xenVersion)
        xenVersion = xenVersion2;
    return(0);
}

/************************************************************************
 *									*
 *	Processing of the unix socket to listen for clients		*
 *									*
 ************************************************************************/

/**
 * proxyCloseUnixSocket:
 *
 * close the unix socket
 *
 * Returns 0 or -1 in case of error
 */
static int
proxyCloseUnixSocket(void) {
    int ret;

    if (fdServer < 0)
        return(0);
    
    ret = close(fdServer);
    if (debug > 0)
        fprintf(stderr, "closing unix socket %d: %d\n", fdServer, ret);
    fdServer = -1;
    pollInfos[0].fd = -1;
    return(ret);
}

/**
 * proxyListenUnixSocket:
 * @path: the fileame for the socket
 *
 * create a new abstract socket based on that path and listen on it
 *
 * Returns the associated file descriptor or -1 in case of failure
 */
static int
proxyListenUnixSocket(const char *path) {
    int fd;
    struct sockaddr_un addr;

    if (fdServer >= 0)
        return(fdServer);

    fd = socket(PF_UNIX, SOCK_STREAM, 0);
    if (fd < 0) {
        fprintf(stderr, "Failed to create unix socket");
	return(-1);
    }

    /*
     * Abstract socket do not hit the filesystem, way more secure and 
     * garanteed to be atomic
     */
    memset(&addr, 0, sizeof(addr));
    addr.sun_family = AF_UNIX;
    addr.sun_path[0] = '\0';
    strncpy(&addr.sun_path[1], path, (sizeof(addr) - 4) - 2);

    /*
     * now bind the socket to that address and listen on it
     */
    if (bind(fd, (struct sockaddr *) &addr, sizeof(addr)) < 0) {
        fprintf(stderr, "Failed to bind to socket %s\n", path);
	close(fd);
	return (-1);
    }
    if (listen(fd, 30 /* backlog */ ) < 0) {
        fprintf(stderr, "Failed to listen to socket %s\n", path);
	close(fd);
	return (-1);
    }

    if (debug > 0)
        fprintf(stderr, "opened and bound unix socket %d\n", fd);

    fdServer = fd;
    pollInfos[0].fd = fd;
    pollInfos[0].events = POLLIN | POLLERR | POLLHUP | POLLNVAL;
    return (fd);
}

/**
 * proxyAcceptClientSocket:
 *
 * Process a request to the unix socket
 *
 * Returns the filedescriptor of the new client or -1 in case of error
 */
static int
proxyAcceptClientSocket(void) {
    int client;
    socklen_t client_addrlen;
    struct sockaddr client_addr;

retry:
    client_addrlen = sizeof(client_addr);
    client = accept(pollInfos[0].fd, &client_addr, &client_addrlen);
    if (client < 0) {
        if (errno == EINTR) {
	    if (debug > 0)
	        fprintf(stderr, "accept connection on socket %d interrupted\n",
		        pollInfos[0].fd);
	    goto retry;
	}
        fprintf(stderr, "Failed to accept incoming connection on socket %d\n",
	        pollInfos[0].fd);
	done = 1;
	return(-1);
    }

    if (nbClients >= MAX_CLIENT) {
        fprintf(stderr, "Too many client registered\n");
	close(client);
	return(-1);
    }
    nbClients++;
    pollInfos[nbClients].fd = client;
    pollInfos[nbClients].events = POLLIN | POLLERR | POLLHUP | POLLNVAL;
    if (debug > 0)
	fprintf(stderr, "accept connection on socket %d for client %d\n",
		client, nbClients);
    return(client);
}

/************************************************************************
 *									*
 *		Processing of client sockets				*
 *									*
 ************************************************************************/

/**
 * proxyCloseClientSocket:
 * @nr: client number
 *
 * Close the socket from that client, and recompact the pollInfo array
 *
 * Returns 0 in case of success and -1 in case of error
 */
static int
proxyCloseClientSocket(int nr) {
    int ret;

    ret = close(pollInfos[nr].fd);
    if (ret != 0)
	fprintf(stderr, "Failed to close socket %d from client %d\n",
	        pollInfos[nr].fd, nr);
    else if (debug > 0)
	fprintf(stderr, "Closed socket %d from client %d\n",
	        pollInfos[nr].fd, nr);
    if (nr < nbClients) {
        memmove(&pollInfos[nr], &pollInfos[nr + 1],
	        (nbClients - nr) * sizeof(pollInfos[0]));
    }
    nbClients--;
    return(ret);
}

/**
 * proxyCloseClientSockets:
 *
 * Close all the sockets from the clients
 */
static void
proxyCloseClientSockets(void) {
    int i, ret;

    for (i = 1;i <= nbClients;i++) {
        ret = close(pollInfos[i].fd);
	if (ret != 0)
	    fprintf(stderr, "Failed to close socket %d from client %d\n",
	            pollInfos[i].fd, i);
	else if (debug > 0)
	    fprintf(stderr, "Closed socket %d from client %d\n",
	            pollInfos[i].fd, i);
    }
    nbClients = 0;
}

/**
 * proxyWriteClientSocket:
 * @nr: the client number
 * @req: pointer to the packet
 *
 * Send back a packet to the client. If it seems write would be blocking
 * then try to disconnect from it.
 *
 * Return 0 in case of success and -1 in case of error.
 */
static int
proxyWriteClientSocket(int nr, virProxyPacketPtr req) {
    int ret;

    if ((nr <= 0) || (nr > nbClients) || (req == NULL) ||
        (req->len < sizeof(virProxyPacket)) || (req->len > 4096) ||
	(pollInfos[nr].fd < 0)) {
	fprintf(stderr, "write to client %d in error", nr);
	proxyCloseClientSocket(nr);
	return(-1);
    }

retry:
    ret = write(pollInfos[nr].fd, (char *) req, req->len);
    if (ret < 0) {
        if (errno == EINTR) {
	    if (debug > 0)
	        fprintf(stderr, "write socket %d to client %d interrupted\n",
		        pollInfos[nr].fd, nr);
	    goto retry;
	}
        fprintf(stderr, "write %d bytes to socket %d from client %d failed\n",
	        req->len, pollInfos[nr].fd, nr);
	proxyCloseClientSocket(nr);
	return(-1);
    }
    if (ret == 0) {
	if (debug)
	    fprintf(stderr, "end of stream from client %d on socket %d\n",
	            nr, pollInfos[nr].fd);
	proxyCloseClientSocket(nr);
	return(-1);
    }

    if (ret != req->len) {
        fprintf(stderr, "write %d of %d bytes to socket %d from client %d\n",
	        ret, req->len, pollInfos[nr].fd, nr);
	proxyCloseClientSocket(nr);
	return(-1);
    }
    if (debug)
        fprintf(stderr, "wrote %d bytes to client %d on socket %d\n",
	        ret, nr, pollInfos[nr].fd);
    
    return(0);
}
/**
 * proxyReadClientSocket:
 * @nr: the client number
 *
 * Process a read from a client socket
 */
static int
proxyReadClientSocket(int nr) {
    char buffer[4096];
    virProxyPacketPtr req;
    int ret;

retry:
    ret = read(pollInfos[nr].fd, buffer, sizeof(virProxyPacket));
    if (ret < 0) {
        if (errno == EINTR) {
	    if (debug > 0)
	        fprintf(stderr, "read socket %d from client %d interrupted\n",
		        pollInfos[nr].fd, nr);
	    goto retry;
	}
        fprintf(stderr, "Failed to read socket %d from client %d\n",
	        pollInfos[nr].fd, nr);
	proxyCloseClientSocket(nr);
	return(-1);
    }
    if (ret == 0) {
	if (debug)
	    fprintf(stderr, "end of stream from client %d on socket %d\n",
	            nr, pollInfos[nr].fd);
	proxyCloseClientSocket(nr);
	return(-1);
    }

    if (debug)
        fprintf(stderr, "read %d bytes from client %d on socket %d\n",
	        ret, nr, pollInfos[nr].fd);
    
    req = (virProxyPacketPtr) &buffer[0];
    if ((req->version != PROXY_PROTO_VERSION) ||
        (req->len < sizeof(virProxyPacket)))
	goto comm_error;
    
    if (debug)
        fprintf(stderr, "Got command %d from client %d\n", req->command, nr);

    switch (req->command) {
	case VIR_PROXY_NONE:
	    if (req->len != sizeof(virProxyPacket))
	        goto comm_error;
	    break;
	case VIR_PROXY_VERSION:
	    if (req->len != sizeof(virProxyPacket))
	        goto comm_error;
	    req->data.larg = xenVersion;
	    break;
	case VIR_PROXY_LIST: {
	    int maxids;

	    if (req->len != sizeof(virProxyPacket))
	        goto comm_error;
	    maxids = (sizeof(buffer) - sizeof(virProxyPacket)) / sizeof(int);
	    maxids -= 10; /* just to be sure that should still be plenty */
	    ret = xenHypervisorListDomains(conn,
	                           (int *) &buffer[sizeof(virProxyPacket)],
				           maxids);
	    if (ret < 0) {
	        req->len = sizeof(virProxyPacket);
		req->data.arg = 0;
	    } else {
	        req->len = sizeof(virProxyPacket) + ret * sizeof(int);
		req->data.arg = ret;
	    }
	    break;
	}
	case VIR_PROXY_NUM_DOMAIN:
	    if (req->len != sizeof(virProxyPacket))
	        goto comm_error;
	    req->data.arg = xenHypervisorNumOfDomains(conn);
	    break;
	case VIR_PROXY_MAX_MEMORY:
	case VIR_PROXY_DOMAIN_INFO:
	case VIR_PROXY_NODE_INFO:
	case VIR_PROXY_LOOKUP_ID:
	case VIR_PROXY_LOOKUP_UUID:
	case VIR_PROXY_LOOKUP_NAME:
	    TODO;
	    break;
	default:
	    goto comm_error;
    }
    ret = proxyWriteClientSocket(nr, req);
    return(ret);

comm_error:
    fprintf(stderr,
	    "Communication error with client %d: malformed packet\n", nr);
    proxyCloseClientSocket(nr);
    return(-1);
}

/************************************************************************
 *									*
 *		Main loop processing					*
 *									*
 ************************************************************************/

/**
 * proxyProcessRequests:
 *
 * process requests and timers 
 */
static void
proxyProcessRequests(void) {
    int exit_timeout = 30;
    int ret, i;

    while (!done) {
        /*
	 * wait for requests, with a one second timeout
	 */
        ret = poll(&pollInfos[0], nbClients + 1, 1000);
	if (ret == 0) { /* timeout */
	    if ((nbClients == 0) && (persist == 0)) {
	        exit_timeout--;
		if (exit_timeout == 0) {
		    done = 1;
		    if (debug > 0) {
		        fprintf(stderr, "Exitting after 30s without clients\n");
		    }
		}
	    } else
	        exit_timeout = 30;
	    if (debug > 1)
	        fprintf(stderr, "poll timeout\n");
	    continue;
	} else if (ret < 0) {
	    if (errno == EINTR) {
	        if (debug > 0)
		    fprintf(stderr, "poll syscall interrupted\n");
		    continue;
	    }
	    fprintf(stderr, "poll syscall failed\n");
	    break;
	}
	/*
	 * there have been I/O to process
	 */
	exit_timeout = 30;
	if (pollInfos[0].revents != 0) {
	    if (pollInfos[0].revents & POLLIN) {
	        proxyAcceptClientSocket();
	    } else {
		fprintf(stderr, "Got an error %d on incoming socket %d\n",
		        pollInfos[0].revents, pollInfos[0].fd);
		break;
	    }
	}

	/*
	 * process the clients in reverse order since on error or disconnect
	 * pollInfos is compacted to remove the given client.
	 */
	for (i = nbClients;i > 0;i--) {
	    if (pollInfos[i].revents & POLLIN) {
		proxyReadClientSocket(i);
	    } else if (pollInfos[i].revents != 0) {
		fprintf(stderr, "Got an error %d on client %d socket %d\n",
		        pollInfos[i].revents, i, pollInfos[i].fd);
		proxyCloseClientSocket(i);
	    }
	}
	    
    }
}

/**
 * proxyMainLoop:
 *
 * main loop for the proxy, continually try to keep the unix socket
 * open, serve client requests, and process timing events.
 */

static void 
proxyMainLoop(void) {
    while (! done) {
	if (proxyListenUnixSocket(PROXY_SOCKET_PATH) < 0)
	    break;
	proxyProcessRequests();
    }
    proxyCloseClientSockets();
}

/**
 * usage:
 *
 * dump on stdout informations about the program
 */
static void
usage(const char *progname) {
    printf("Usage: %s [-v] [-v]\n", progname);
    printf("    option -v increase the verbosity level for debugging\n");
    printf("This is a proxy for xen services used by libvirt to offer\n");
    printf("safe and fast status information on the Xen virtualization.\n");
    printf("This need not be run manually it's started automatically.\n");
}

/**
 * main:
 *
 * Check that we are running with root priviledges, initialize the
 * connections to the daemon and or hypervisor, and then run the main loop
 */
int main(int argc, char **argv) {
    int i;

    for (i = 1; i < argc; i++) {
         if (!strcmp(argv[i], "-v")) {
	     debug++;
         } else if (!strcmp(argv[i], "-no-timeout")) {
	     persist = 1;
	 } else {
	     usage(argv[0]);
	     exit(1);
	 }
    }
    
    if (geteuid() != 0) {
        fprintf(stderr, "%s must be run as root or suid\n", argv[0]);
	/* exit(1); */
    }

    /*
     * setup a connection block
     */
    memset(conn, 0, sizeof(conninfos));
    conn->magic = VIR_CONNECT_MAGIC;

    /*
     * very fist thing, use the socket as an exclusive lock, this then
     * allow to do timed exits, avoiding constant CPU usage in case of
     * failure.
     */
    if (proxyListenUnixSocket(PROXY_SOCKET_PATH) < 0)
        exit(0);
    if (proxyInitXen() == 0)
	proxyMainLoop();
    sleep(1);
    proxyCloseUnixSocket();
    exit(0);
}