net_unix.h

/*
Copyright (C) 2012 skuller.net

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.

This program 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 General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.

*/

//
// net_unix.h -- BSD sockets wrapper
//

static const char *os_error_string(int err)
{
    return strerror(err);
}

// Receiving ICMP errors on unconnected UDP sockets is tricky...
// Linux 2.2 and higher supports this via IP_RECVERR option, see ip(7).
// What about BSD?

#ifdef __linux__

static qboolean check_offender(const struct sockaddr_in *from,
                               const struct sockaddr_in *to)
{
    if (!to)
        return qfalse;

    if (from->sin_addr.s_addr != to->sin_addr.s_addr)
        return qfalse;

    if (from->sin_port && from->sin_port != to->sin_port)
        return qfalse;

    Com_DPrintf("%s: found offending address %s:%d\n", "process_error_queue",
                inet_ntoa(from->sin_addr), ntohs(from->sin_port));

    return qtrue;
}

// Returns true if failed socket operation should be retried.
// May get called from NET_SendPacket() path, avoid interfering with net_from.
static qboolean process_error_queue(netsrc_t sock, const struct sockaddr_in *to_addr)
{
    byte buffer[1024];
    struct sockaddr_in from_addr;
    struct msghdr msg;
    struct cmsghdr *cmsg;
    struct sock_extended_err *ee;
    netadr_t from;
    int tries;
    qboolean found = qfalse;

    for (tries = 0; tries < MAX_ERROR_RETRIES; tries++) {
        memset(&from_addr, 0, sizeof(from_addr));

        memset(&msg, 0, sizeof(msg));
        msg.msg_name = &from_addr;
        msg.msg_namelen = sizeof(from_addr);
        msg.msg_control = buffer;
        msg.msg_controllen = sizeof(buffer);

        if (recvmsg(udp_sockets[sock], &msg, MSG_ERRQUEUE) == -1) {
            if (errno != EWOULDBLOCK)
                Com_DPrintf("%s: %s\n", __func__, strerror(errno));
            break;
        }

        if (!(msg.msg_flags & MSG_ERRQUEUE)) {
            Com_DPrintf("%s: no extended error received\n", __func__);
            break;
        }

        // find an ICMP error message
        for (cmsg = CMSG_FIRSTHDR(&msg);
             cmsg != NULL;
             cmsg = CMSG_NXTHDR(&msg, cmsg)) {
            if (cmsg->cmsg_level != IPPROTO_IP) {
                continue;
            }
            if (cmsg->cmsg_type != IP_RECVERR) {
                continue;
            }
            ee = (struct sock_extended_err *)CMSG_DATA(cmsg);
            if (ee->ee_origin == SO_EE_ORIGIN_ICMP) {
                break;
            }
        }

        if (!cmsg) {
            Com_DPrintf("%s: no ICMP error found\n", __func__);
            break;
        }

        found |= check_offender(&from_addr, to_addr);

        NET_SockadrToNetadr(&from_addr, &from);

        // handle ICMP error
        NET_ErrorEvent(sock, &from, ee->ee_errno, ee->ee_info);
    }

    return !!tries && !found;
}

#endif // !__linux__

static ssize_t os_udp_recv(netsrc_t sock, void *data,
                           size_t len, netadr_t *from)
{
    struct sockaddr_in addr;
    socklen_t addrlen;
    ssize_t ret;

#ifdef __linux__
    int tries;
    for (tries = 0; tries < MAX_ERROR_RETRIES; tries++) {
#endif
        memset(&addr, 0, sizeof(addr));
        addrlen = sizeof(addr);
        ret = recvfrom(udp_sockets[sock], data, len, 0,
                       (struct sockaddr *)&addr, &addrlen);

        NET_SockadrToNetadr(&addr, from);

        if (ret >= 0)
            return ret;

        net_error = errno;

        // wouldblock is silent
        if (net_error == EWOULDBLOCK)
            return NET_AGAIN;

#ifdef __linux__
        // recvfrom() fails on Linux if there is an ICMP originated pending
        // error on socket. Suck up error queue and retry...

        if (!process_error_queue(sock, NULL))
            break;
    }
#endif

    return NET_ERROR;
}

static ssize_t os_udp_send(netsrc_t sock, const void *data,
                           size_t len, const netadr_t *to)
{
    struct sockaddr_in addr;
    ssize_t ret;

    NET_NetadrToSockadr(to, &addr);

#ifdef __linux__
    int tries;
    for (tries = 0; tries < MAX_ERROR_RETRIES; tries++) {
#endif
        ret = sendto(udp_sockets[sock], data, len, 0,
                     (struct sockaddr *)&addr, sizeof(addr));
        if (ret >= 0)
            return ret;

        net_error = errno;

        // wouldblock is silent
        if (net_error == EWOULDBLOCK)
            return NET_AGAIN;

#ifdef __linux__
        // sendto() fails on Linux if there is an ICMP originated pending error
        // on socket. Suck up error queue and retry...
        //
        // But how do I distingiush between a failure caused by completely
        // unrelated ICMP error sitting in the queue and an error directly
        // related to this sendto() call?
        //
        // On one hand, I don't want to drop packets to legitimate clients, and
        // have to retry sendto() after processing error queue. On other
        // hand, infinite loop should be avoided if sendto() call regenerates
        // the message in error queue.
        //
        // This mess is worked around by passing destination address to
        // process_error_queue() and checking if this address/port pair is
        // found in the queue. If it is found, or the queue is empty, do not
        // retry.

        if (!process_error_queue(sock, &addr))
            break;
    }
#endif

    return NET_ERROR;
}

static neterr_t os_get_error(void)
{
    net_error = errno;
    if (net_error == EWOULDBLOCK)
        return NET_AGAIN;

    return NET_ERROR;
}

static ssize_t os_recv(qsocket_t sock, void *data, size_t len, int flags)
{
    ssize_t ret = recv(sock, data, len, flags);

    if (ret == -1)
        return os_get_error();

    return ret;
}

static ssize_t os_send(qsocket_t sock, const void *data, size_t len, int flags)
{
    ssize_t ret = send(sock, data, len, flags);

    if (ret == -1)
        return os_get_error();

    return ret;
}

static neterr_t os_listen(qsocket_t sock, int backlog)
{
    if (listen(sock, backlog) == -1) {
        net_error = errno;
        return NET_ERROR;
    }

    return NET_OK;
}

static neterr_t os_accept(qsocket_t sock, qsocket_t *newsock, netadr_t *from)
{
    struct sockaddr_in addr;
    socklen_t addrlen;
    int s;

    memset(&addr, 0, sizeof(addr));
    addrlen = sizeof(addr);
    s = accept(sock, (struct sockaddr *)&addr, &addrlen);

    NET_SockadrToNetadr(&addr, from);

    if (s == -1) {
        *newsock = -1;
        return os_get_error();
    }

    *newsock = s;
    return NET_OK;
}

static neterr_t os_connect(qsocket_t sock, const netadr_t *to)
{
    struct sockaddr_in addr;

    NET_NetadrToSockadr(to, &addr);

    if (connect(sock, (struct sockaddr *)&addr, sizeof(addr)) == -1) {
        net_error = errno;
        if (net_error == EINPROGRESS)
            return NET_OK;

        return NET_ERROR;
    }

    return NET_OK;
}

static neterr_t os_make_nonblock(qsocket_t sock, int val)
{
    if (ioctl(sock, FIONBIO, &val) == -1) {
        net_error = errno;
        return NET_ERROR;
    }

    return NET_OK;
}

static neterr_t os_setsockopt(qsocket_t sock, int level, int name, int val)
{
    if (setsockopt(sock, level, name, &val, sizeof(val)) == -1) {
        net_error = errno;
        return NET_ERROR;
    }

    return NET_OK;
}

static neterr_t os_getsockopt(qsocket_t sock, int level, int name, int *val)
{
    socklen_t _optlen = sizeof(*val);

    if (getsockopt(sock, level, name, val, &_optlen) == -1) {
        net_error = errno;
        return NET_ERROR;
    }

    return NET_OK;
}

static neterr_t os_bind(qsocket_t sock, const struct sockaddr *addr, size_t addrlen)
{
    if (bind(sock, addr, addrlen) == -1) {
        net_error = errno;
        return NET_ERROR;
    }

    return NET_OK;
}

static neterr_t os_getsockname(qsocket_t sock, netadr_t *name)
{
    struct sockaddr_in addr;
    socklen_t addrlen;

    memset(&addr, 0, sizeof(addr));
    addrlen = sizeof(addr);
    if (getsockname(sock, (struct sockaddr *)&addr, &addrlen) == -1) {
        net_error = errno;
        return NET_ERROR;
    }

    NET_SockadrToNetadr(&addr, name);
    return NET_OK;
}

static void os_closesocket(qsocket_t sock)
{
    close(sock);
}

static qsocket_t os_socket(int domain, int type, int protocol)
{
    int s = socket(domain, type, protocol);

    if (s == -1) {
        net_error = errno;
        return -1;
    }

    return s;
}

static ioentry_t *_os_get_io(qsocket_t fd, const char *func)
{
    if (fd < 0 || fd >= FD_SETSIZE)
        Com_Error(ERR_FATAL, "%s: fd out of range: %d", func, fd);

    return &io_entries[fd];
}

static ioentry_t *os_add_io(qsocket_t fd)
{
    if (fd >= io_numfds) {
        io_numfds = fd + 1;
    }

    return _os_get_io(fd, __func__);
}

static ioentry_t *os_get_io(qsocket_t fd)
{
    return _os_get_io(fd, __func__);
}

static qsocket_t os_get_fd(ioentry_t *e)
{
    return e - io_entries;
}

static int os_select(int nfds, fd_set *rfds, fd_set *wfds,
                     fd_set *efds, struct timeval *tv)
{
    int ret = select(nfds, rfds, wfds, efds, tv);

    if (ret == -1) {
        net_error = errno;
        if (net_error == EINTR)
            return 0;
    }

    return ret;
}

static void os_net_init(void)
{
}

static void os_net_shutdown(void)
{
}