sctp.c

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/*
 * SCTP protocol
 * Copyright (c) 2012 Luca Barbato
 *
 * This file is part of Libav.
 *
 * Libav is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * Libav is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with Libav; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

/**
 * @file
 *
 * sctp url_protocol
 *
 * url syntax: sctp://host:port[?option=val...]
 * option: 'listen'        : listen for an incoming connection
 *         'max_streams=n' : set the maximum number of streams
 *         'reuse=1'       : enable reusing the socket [TBD]
 *
 * by setting the maximum number of streams the protocol will use the
 * first two bytes of the incoming/outgoing buffer to store the
 * stream number of the packet being read/written.
 * @see sctp_read
 * @see sctp_write
 */


#include <netinet/in.h>
#include <netinet/sctp.h>

#include "config.h"

#if HAVE_POLL_H
#include <poll.h>
#endif

#include "libavutil/intreadwrite.h"
#include "libavutil/parseutils.h"
#include "avformat.h"
#include "internal.h"
#include "network.h"
#include "os_support.h"
#include "url.h"

/*
 * The sctp_recvmsg and sctp_sendmsg functions are part of the user
 * library that offers support for the SCTP kernel Implementation.
 * To avoid build-time clashes the functions sport an ff_-prefix here.
 * The main purpose of this code is to provide the SCTP Socket API
 * mappings for user applications to interface with SCTP in the kernel.
 *
 * This implementation is based on the Socket API Extensions for SCTP
 * defined in <draft-ietf-tsvwg-sctpsocket-10.txt>
 *
 * Copyright (c) 2003 International Business Machines, Corp.
 *
 * Written or modified by:
 *  Ryan Layer <rmlayer@us.ibm.com>
 */

static int ff_sctp_recvmsg(int s, void *msg, size_t len, struct sockaddr *from,
                           socklen_t *fromlen, struct sctp_sndrcvinfo *sinfo,
                           int *msg_flags)
{
    int recvb;
    struct iovec iov;
    char incmsg[CMSG_SPACE(sizeof(struct sctp_sndrcvinfo))];
    struct msghdr inmsg  = { 0 };
    struct cmsghdr *cmsg = NULL;

    iov.iov_base = msg;
    iov.iov_len  = len;

    inmsg.msg_name       = from;
    inmsg.msg_namelen    = fromlen ? *fromlen : 0;
    inmsg.msg_iov        = &iov;
    inmsg.msg_iovlen     = 1;
    inmsg.msg_control    = incmsg;
    inmsg.msg_controllen = sizeof(incmsg);

    if ((recvb = recvmsg(s, &inmsg, msg_flags ? *msg_flags : 0)) < 0)
        return recvb;

    if (fromlen)
        *fromlen   = inmsg.msg_namelen;
    if (msg_flags)
        *msg_flags = inmsg.msg_flags;

    for (cmsg = CMSG_FIRSTHDR(&inmsg); cmsg != NULL;
         cmsg = CMSG_NXTHDR(&inmsg, cmsg)) {
        if ((IPPROTO_SCTP == cmsg->cmsg_level) &&
            (SCTP_SNDRCV  == cmsg->cmsg_type))
            break;
    }

    /* Copy sinfo. */
    if (cmsg)
        memcpy(sinfo, CMSG_DATA(cmsg), sizeof(struct sctp_sndrcvinfo));

    return recvb;
}

static int ff_sctp_send(int s, const void *msg, size_t len,
                        const struct sctp_sndrcvinfo *sinfo, int flags)
{
    struct msghdr outmsg;
    struct iovec iov;

    outmsg.msg_name       = NULL;
    outmsg.msg_namelen    = 0;
    outmsg.msg_iov        = &iov;
    iov.iov_base          = (void*)msg;
    iov.iov_len           = len;
    outmsg.msg_iovlen     = 1;
    outmsg.msg_controllen = 0;

    if (sinfo) {
        char outcmsg[CMSG_SPACE(sizeof(struct sctp_sndrcvinfo))];
        struct cmsghdr *cmsg;

        outmsg.msg_control    = outcmsg;
        outmsg.msg_controllen = sizeof(outcmsg);
        outmsg.msg_flags      = 0;

        cmsg             = CMSG_FIRSTHDR(&outmsg);
        cmsg->cmsg_level = IPPROTO_SCTP;
        cmsg->cmsg_type  = SCTP_SNDRCV;
        cmsg->cmsg_len   = CMSG_LEN(sizeof(struct sctp_sndrcvinfo));

        outmsg.msg_controllen = cmsg->cmsg_len;
        memcpy(CMSG_DATA(cmsg), sinfo, sizeof(struct sctp_sndrcvinfo));
    }

    return sendmsg(s, &outmsg, flags);
}

typedef struct SCTPContext {
    int fd;
    int max_streams;
    struct sockaddr_storage dest_addr;
    socklen_t dest_addr_len;
} SCTPContext;

static int sctp_open(URLContext *h, const char *uri, int flags)
{
    struct addrinfo *ai, *cur_ai;
    struct addrinfo hints             = { 0 };
    struct sctp_event_subscribe event = { 0 };
    struct sctp_initmsg initparams    = { 0 };
    int port;
    int fd         = -1;
    SCTPContext *s = h->priv_data;
    const char *p;
    char buf[256];
    int ret, listen_socket = 0;
    char hostname[1024], proto[1024], path[1024];
    char portstr[10];

    av_url_split(proto, sizeof(proto), NULL, 0, hostname, sizeof(hostname),
                 &port, path, sizeof(path), uri);
    if (strcmp(proto, "sctp"))
        return AVERROR(EINVAL);
    if (port <= 0 || port >= 65536) {
        av_log(s, AV_LOG_ERROR, "Port missing in uri\n");
        return AVERROR(EINVAL);
    }

    s->max_streams = 0;
    p = strchr(uri, '?');
    if (p) {
        if (av_find_info_tag(buf, sizeof(buf), "listen", p))
            listen_socket = 1;
        if (av_find_info_tag(buf, sizeof(buf), "max_streams", p))
            s->max_streams = strtol(buf, NULL, 10);
    }

    hints.ai_family   = AF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;
    snprintf(portstr, sizeof(portstr), "%d", port);
    ret = getaddrinfo(hostname, portstr, &hints, &ai);
    if (ret) {
        av_log(h, AV_LOG_ERROR, "Failed to resolve hostname %s: %s\n",
               hostname, gai_strerror(ret));
        return AVERROR(EIO);
    }

    cur_ai = ai;

    fd = socket(cur_ai->ai_family, SOCK_STREAM, IPPROTO_SCTP);
    if (fd < 0)
        goto fail;

    s->dest_addr_len = sizeof(s->dest_addr);

    if (listen_socket) {
        int fd1;
        ret = bind(fd, cur_ai->ai_addr, cur_ai->ai_addrlen);
        listen(fd, 100);
        fd1 = accept(fd, NULL, NULL);
        closesocket(fd);
        fd  = fd1;
    } else
        ret = connect(fd, cur_ai->ai_addr, cur_ai->ai_addrlen);

    ff_socket_nonblock(fd, 1);

    event.sctp_data_io_event = 1;
    /* TODO: Subscribe to more event types and handle them */

    if (setsockopt(fd, IPPROTO_SCTP, SCTP_EVENTS, &event,
                   sizeof(event)) != 0) {
        av_log(h, AV_LOG_ERROR,
               "SCTP ERROR: Unable to subscribe to events\n");
        goto fail;
    }

    if (s->max_streams) {
        initparams.sinit_max_instreams = s->max_streams;
        initparams.sinit_num_ostreams  = s->max_streams;
        if (setsockopt(fd, IPPROTO_SCTP, SCTP_INITMSG, &initparams,
                       sizeof(initparams)) < 0)
            av_log(h, AV_LOG_ERROR,
                   "SCTP ERROR: Unable to initialize socket max streams %d\n",
                   s->max_streams);
    }

    h->priv_data   = s;
    h->is_streamed = 1;
    s->fd          = fd;
    freeaddrinfo(ai);
    return 0;

fail:
    ret = AVERROR(EIO);
    freeaddrinfo(ai);
    return ret;
}

static int sctp_wait_fd(int fd, int write)
{
    int ev          = write ? POLLOUT : POLLIN;
    struct pollfd p = { .fd = fd, .events = ev, .revents = 0 };
    int ret;

    ret = poll(&p, 1, 100);
    return ret < 0 ? ff_neterrno() : p.revents & ev ? 0 : AVERROR(EAGAIN);
}

static int sctp_read(URLContext *h, uint8_t *buf, int size)
{
    SCTPContext *s = h->priv_data;
    int ret;

    if (!(h->flags & AVIO_FLAG_NONBLOCK)) {
        ret = sctp_wait_fd(s->fd, 0);
        if (ret < 0)
            return ret;
    }

    if (s->max_streams) {
        /*StreamId is introduced as a 2byte code into the stream*/
        struct sctp_sndrcvinfo info = { 0 };
        ret = ff_sctp_recvmsg(s->fd, buf + 2, size - 2, NULL, 0, &info, 0);
        AV_WB16(buf, info.sinfo_stream);
        ret = ret < 0 ? ret : ret + 2;
    } else
        ret = recv(s->fd, buf, size, 0);

    return ret < 0 ? ff_neterrno() : ret;
}

static int sctp_write(URLContext *h, const uint8_t *buf, int size)
{
    SCTPContext *s = h->priv_data;
    int ret;

    if (!(h->flags & AVIO_FLAG_NONBLOCK)) {
        ret = sctp_wait_fd(s->fd, 1);
        if (ret < 0)
            return ret;
    }

    if (s->max_streams) {
        /*StreamId is introduced as a 2byte code into the stream*/
        struct sctp_sndrcvinfo info = { 0 };
        info.sinfo_stream           = AV_RB16(buf);
        if (info.sinfo_stream > s->max_streams) {
            av_log(h, AV_LOG_ERROR, "bad input data\n");
            return AVERROR(EINVAL);
        }
        ret = ff_sctp_send(s->fd, buf + 2, size - 2, &info, MSG_EOR);
    } else
        ret = send(s->fd, buf, size, 0);

    return ret < 0 ? ff_neterrno() : ret;
}

static int sctp_close(URLContext *h)
{
    SCTPContext *s = h->priv_data;
    closesocket(s->fd);
    return 0;
}

static int sctp_get_file_handle(URLContext *h)
{
    SCTPContext *s = h->priv_data;
    return s->fd;
}

URLProtocol ff_sctp_protocol = {
    .name                = "sctp",
    .url_open            = sctp_open,
    .url_read            = sctp_read,
    .url_write           = sctp_write,
    .url_close           = sctp_close,
    .url_get_file_handle = sctp_get_file_handle,
    .priv_data_size      = sizeof(SCTPContext),
    .flags               = URL_PROTOCOL_FLAG_NETWORK,
};