openflow/lib/dpif.c

/* Copyright (c) 2008, 2009 The Board of Trustees of The Leland Stanford
 * Junior University
 * 
 * We are making the OpenFlow specification and associated documentation
 * (Software) available for public use and benefit with the expectation
 * that others will use, modify and enhance the Software and contribute
 * those enhancements back to the community. However, since we would
 * like to make the Software available for broadest use, with as few
 * restrictions as possible permission is hereby granted, free of
 * charge, to any person obtaining a copy of this Software to deal in
 * the Software under the copyrights without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 * 
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT.  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 * 
 * The name and trademarks of copyright holder(s) may NOT be used in
 * advertising or publicity pertaining to the Software or any
 * derivatives without specific, written prior permission.
 */

#include <config.h>
#include "dpif.h"

#include <assert.h>
#include <ctype.h>
#include <errno.h>
#include <inttypes.h>
#include <netinet/in.h>
#include <stdlib.h>
#include <string.h>

#include "netlink.h"
#include "netlink-protocol.h"
#include "ofpbuf.h"
#include "openflow/openflow-netlink.h"
#include "openflow/openflow.h"
#include "packets.h"
#include "util.h"
#include "xtoxll.h"

#include "vlog.h"
#define THIS_MODULE VLM_dpif

/* Not really much point in logging many dpif errors. */
static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(5, 60);

/* The Generic Netlink family number used for OpenFlow. */
static int openflow_family;

static int lookup_openflow_multicast_group(int dp_idx, int *multicast_group);
static int send_mgmt_command(struct dpif *, int dp_idx, int command,
                             const char *netdev);

/* Opens a socket for a local datapath, initializing 'dp'.  If
 * 'subscribe_dp_idx' is nonnegative, listens for asynchronous messages
 * (packet-in, etc.) from the datapath with that number; otherwise, 'dp' will
 * receive only replies to explicitly initiated requests. */
int
dpif_open(int subscribe_dp_idx, struct dpif *dp)
{
    struct nl_sock *sock;
    int multicast_group = 0;
    int retval;

    retval = nl_lookup_genl_family(DP_GENL_FAMILY_NAME, &openflow_family);
    if (retval) {
        return retval;
    }

    if (subscribe_dp_idx >= 0) {
        retval = lookup_openflow_multicast_group(subscribe_dp_idx,
                                                 &multicast_group);
        if (retval) {
            return retval;
        }
    }

    /* Specify a large so_rcvbuf size because we occasionally need to be able
     * to retrieve large collections of flow records. */
    retval = nl_sock_create(NETLINK_GENERIC, multicast_group, 0,
                            4 * 1024u * 1024, &sock);
    if (retval) {
        return retval;
    }

    dp->sock = sock;
    return 0;
}

/* Closes 'dp'. */
void
dpif_close(struct dpif *dp) 
{
    if (dp) {
        nl_sock_destroy(dp->sock);
    }
}

static const struct nl_policy openflow_policy[] = {
    [DP_GENL_A_DP_IDX] = { .type = NL_A_U32,
                           .optional = false },
    [DP_GENL_A_OPENFLOW] = { .type = NL_A_UNSPEC,
                             .min_len = sizeof(struct ofp_header),
                             .max_len = 65535,
                             .optional = false },
};

/* Tries to receive an openflow message from datapath 'dp_idx' on 'sock'.  If
 * successful, stores the received message into '*msgp' and returns 0.  The
 * caller is responsible for destroying the message with ofpbuf_delete().  On
 * failure, returns a positive errno value and stores a null pointer into
 * '*msgp'.
 *
 * Only Netlink messages with embedded OpenFlow messages are accepted.  Other
 * Netlink messages provoke errors.
 *
 * If 'wait' is true, dpif_recv_openflow waits for a message to be ready;
 * otherwise, returns EAGAIN if the 'sock' receive buffer is empty. */
int
dpif_recv_openflow(struct dpif *dp, int dp_idx, struct ofpbuf **bufferp,
                   bool wait)
{
    struct nlattr *attrs[ARRAY_SIZE(openflow_policy)];
    struct ofpbuf *buffer;
    struct ofp_header *oh;
    uint16_t ofp_len;

    buffer = *bufferp = NULL;
    do {
        int retval;

        do {
            ofpbuf_delete(buffer);
            retval = nl_sock_recv(dp->sock, &buffer, wait);
        } while (retval == ENOBUFS
                 || (!retval
                     && (nl_msg_nlmsghdr(buffer)->nlmsg_type == NLMSG_DONE
                         || nl_msg_nlmsgerr(buffer, NULL))));
        if (retval) {
            if (retval != EAGAIN) {
                VLOG_WARN_RL(&rl, "dpif_recv_openflow: %s", strerror(retval));
            }
            return retval;
        }

        if (nl_msg_genlmsghdr(buffer) == NULL) {
            VLOG_DBG_RL(&rl, "received packet too short for Generic Netlink");
            goto error;
        }
        if (nl_msg_nlmsghdr(buffer)->nlmsg_type != openflow_family) {
            VLOG_DBG_RL(&rl,
                        "received type (%"PRIu16") != openflow family (%d)",
                        nl_msg_nlmsghdr(buffer)->nlmsg_type, openflow_family);
            goto error;
        }

        if (!nl_policy_parse(buffer, NLMSG_HDRLEN + GENL_HDRLEN,
                             openflow_policy, attrs,
                             ARRAY_SIZE(openflow_policy))) {
            goto error;
        }
    } while (nl_attr_get_u32(attrs[DP_GENL_A_DP_IDX]) != dp_idx);

    oh = buffer->data = (void *) nl_attr_get(attrs[DP_GENL_A_OPENFLOW]);
    buffer->size = nl_attr_get_size(attrs[DP_GENL_A_OPENFLOW]);
    ofp_len = ntohs(oh->length);
    if (ofp_len != buffer->size) {
        VLOG_WARN_RL(&rl,
                     "ofp_header.length %"PRIu16" != attribute length %zu\n",
                     ofp_len, buffer->size);
        buffer->size = MIN(ofp_len, buffer->size);
    }
    *bufferp = buffer;
    return 0;

error:
    ofpbuf_delete(buffer);
    return EPROTO;
}

/* Encapsulates 'msg', which must contain an OpenFlow message, in a Netlink
 * message, and sends it to the OpenFlow local datapath numbered 'dp_idx' via
 * 'sock'.
 *
 * Returns 0 if successful, otherwise a positive errno value.  Returns EAGAIN
 * if the 'sock' send buffer is full.
 *
 * If the send is successful, then the kernel module will receive it, but there
 * is no guarantee that any reply will not be dropped (see nl_sock_transact()
 * for details). 
 */
int
dpif_send_openflow(struct dpif *dp, int dp_idx, struct ofpbuf *buffer)
{
    struct ofp_header *oh;
    unsigned int dump_flag;
    struct ofpbuf hdr;
    struct nlattr *nla;
    uint32_t fixed_buffer[64 / 4];
    struct iovec iov[3];
    int pad_bytes;
    int n_iov;
    int retval;

    /* The reply to OFPT_STATS_REQUEST may be multiple segments long, so we
     * need to specify NLM_F_DUMP in the request. */
    oh = ofpbuf_at_assert(buffer, 0, sizeof *oh);
    dump_flag = oh->type == OFPT_STATS_REQUEST ? NLM_F_DUMP : 0;

    ofpbuf_use(&hdr, fixed_buffer, sizeof fixed_buffer);
    nl_msg_put_genlmsghdr(&hdr, dp->sock, 32, openflow_family,
                          NLM_F_REQUEST | dump_flag, DP_GENL_C_OPENFLOW, 1);
    nl_msg_put_u32(&hdr, DP_GENL_A_DP_IDX, dp_idx);
    nla = ofpbuf_put_uninit(&hdr, sizeof *nla);
    nla->nla_len = sizeof *nla + buffer->size;
    nla->nla_type = DP_GENL_A_OPENFLOW;
    pad_bytes = NLA_ALIGN(nla->nla_len) - nla->nla_len;
    nl_msg_nlmsghdr(&hdr)->nlmsg_len = hdr.size + buffer->size + pad_bytes;
    n_iov = 2;
    iov[0].iov_base = hdr.data;
    iov[0].iov_len = hdr.size;
    iov[1].iov_base = buffer->data;
    iov[1].iov_len = buffer->size;
    if (pad_bytes) {
        static char zeros[NLA_ALIGNTO];
        n_iov++;
        iov[2].iov_base = zeros;
        iov[2].iov_len = pad_bytes; 
    }
    retval = nl_sock_sendv(dp->sock, iov, n_iov, false);
    if (retval && retval != EAGAIN) {
        VLOG_WARN_RL(&rl, "dpif_send_openflow: %s", strerror(retval));
    }
    return retval;
}

/* Creates local datapath numbered 'dp_idx' with the name 'dp_name'.  A
 * 'dp_idx' of -1 or null 'dp_name' will have the kernel module choose values.
 * (At least one or the other must be provided, however, so that the caller can
 * identify the datapath that was created.)  Returns 0 if successful, otherwise
 * a positive errno value. */
int
dpif_add_dp(struct dpif *dp, int dp_idx, const char *dp_name)
{
    return send_mgmt_command(dp, dp_idx, DP_GENL_C_ADD_DP, dp_name);
}

/* Destroys a local datapath.  If 'dp_idx' is not -1, destroys the datapath
 * with that number; if 'dp_name' is not NULL, destroys the datapath with that
 * name.  Exactly one of 'dp_idx' and 'dp_name' should be used.  Returns 0 if
 * successful, otherwise a positive errno value. */
int
dpif_del_dp(struct dpif *dp, int dp_idx, const char *dp_name)
{
    return send_mgmt_command(dp, dp_idx, DP_GENL_C_DEL_DP, dp_name);
}

/* Adds the Ethernet device named 'netdev' to the local datapath numbered
 * 'dp_idx'.  Returns 0 if successful, otherwise a positive errno value. */
int
dpif_add_port(struct dpif *dp, int dp_idx, const char *netdev)
{
    return send_mgmt_command(dp, dp_idx, DP_GENL_C_ADD_PORT, netdev);
}

/* Removes the Ethernet device named 'netdev' from the local datapath numbered
 * 'dp_idx'.  Returns 0 if successful, otherwise a positive errno value. */
int
dpif_del_port(struct dpif *dp, int dp_idx, const char *netdev)
{
    return send_mgmt_command(dp, dp_idx, DP_GENL_C_DEL_PORT, netdev);
}

static const struct nl_policy openflow_multicast_policy[] = {
    [DP_GENL_A_DP_IDX] = { .type = NL_A_U32 },
    [DP_GENL_A_DP_NAME] = { .type = NL_A_STRING },
    [DP_GENL_A_MC_GROUP] = { .type = NL_A_U32 },
};

/* Looks up the Netlink multicast group and datapath index of a datapath
 * by either the datapath index or name.  If 'dp_idx' points to a value 
 * of '-1', then 'dp_name' is used to lookup the datapath.  If successful, 
 * stores the multicast group in '*multicast_group' and the index in
 * '*dp_idx' and returns 0. Otherwise, returns a positive errno value. */
static int
query_datapath(int *dp_idx, int *multicast_group, const char *dp_name)
{
    struct nl_sock *sock;
    struct ofpbuf request, *reply;
    struct nlattr *attrs[ARRAY_SIZE(openflow_multicast_policy)];
    int retval;

    retval = nl_sock_create(NETLINK_GENERIC, 0, 0, 0, &sock);
    if (retval) {
        return retval;
    }
    ofpbuf_init(&request, 0);
    nl_msg_put_genlmsghdr(&request, sock, 0, openflow_family, NLM_F_REQUEST,
                          DP_GENL_C_QUERY_DP, 1);
    if (*dp_idx != -1) {
        nl_msg_put_u32(&request, DP_GENL_A_DP_IDX, *dp_idx);
    }
    if (dp_name) {
        nl_msg_put_string(&request, DP_GENL_A_DP_NAME, dp_name);
    }
    retval = nl_sock_transact(sock, &request, &reply);
    ofpbuf_uninit(&request);
    if (retval) {
        nl_sock_destroy(sock);
        return retval;
    }
    if (!nl_policy_parse(reply, NLMSG_HDRLEN + GENL_HDRLEN,
                         openflow_multicast_policy, attrs,
                         ARRAY_SIZE(openflow_multicast_policy))) {
        nl_sock_destroy(sock);
        ofpbuf_delete(reply);
        return EPROTO;
    }
    *dp_idx = nl_attr_get_u32(attrs[DP_GENL_A_DP_IDX]);
    *multicast_group = nl_attr_get_u32(attrs[DP_GENL_A_MC_GROUP]);
    nl_sock_destroy(sock);
    ofpbuf_delete(reply);

    return 0;
}

/* Looks up the Netlink multicast group used by datapath 'dp_idx'.  If
 * successful, stores the multicast group in '*multicast_group' and returns 0.
 * Otherwise, returns a positve errno value. */
static int
lookup_openflow_multicast_group(int dp_idx, int *multicast_group)
{
    return query_datapath(&dp_idx, multicast_group, NULL);
}

/* Looks up the datatpath index based on the name.  Returns the index, or
 * -1 on error. */
int
dpif_get_idx(const char *name)
{
    int dp_idx = -1;
    int mc_group = 0;

    if (query_datapath(&dp_idx, &mc_group, name)) {
        return -1;
    }

    return dp_idx;
}

/* Sends the given 'command' to datapath 'dp', related to the local datapath
 * numbered 'dp_idx'.  If 'arg' is nonnull, adds it to the command as the
 * datapath or port name attribute depending on the requested operation.  
 * Returns 0 if successful, otherwise a positive errno value. */
static int
send_mgmt_command(struct dpif *dp, int dp_idx, int command, const char *arg)
{
    struct ofpbuf request, *reply;
    int retval;

    ofpbuf_init(&request, 0);
    nl_msg_put_genlmsghdr(&request, dp->sock, 32, openflow_family,
                          NLM_F_REQUEST | NLM_F_ACK, command, 1);
    if (dp_idx != -1) {
        nl_msg_put_u32(&request, DP_GENL_A_DP_IDX, dp_idx);
    }
    if (arg) {
        if ((command == DP_GENL_C_ADD_DP) || (command == DP_GENL_C_DEL_DP)) {
            nl_msg_put_string(&request, DP_GENL_A_DP_NAME, arg);
        } else {
            nl_msg_put_string(&request, DP_GENL_A_PORTNAME, arg);
        }
    }
    retval = nl_sock_transact(dp->sock, &request, &reply);
    ofpbuf_uninit(&request);
    ofpbuf_delete(reply);

    return retval;
}