githubmirror/libslirp

misc.c
298 строк9 KB
Peter Maydell
slirp: fork_exec(): create and connect child socket before fork()
10 ноя 2018, 17:07
10 ноя 2018, 17:07d8730f8
/*
 * Copyright (c) 1995 Danny Gasparovski.
 *
 * Please read the file COPYRIGHT for the
 * terms and conditions of the copyright.
 */

#include "qemu/osdep.h"
#include "slirp.h"
#include "libslirp.h"
#include "monitor/monitor.h"
#include "qemu/error-report.h"
#include "qemu/main-loop.h"

#ifdef DEBUG
int slirp_debug = DBG_CALL | DBG_MISC | DBG_ERROR;
#endif

inline void insque(void *a, void *b)
{
    register struct quehead *element = (struct quehead *)a;
    register struct quehead *head = (struct quehead *)b;
    element->qh_link = head->qh_link;
    head->qh_link = (struct quehead *)element;
    element->qh_rlink = (struct quehead *)head;
    ((struct quehead *)(element->qh_link))->qh_rlink =
        (struct quehead *)element;
}

inline void remque(void *a)
{
    register struct quehead *element = (struct quehead *)a;
    ((struct quehead *)(element->qh_link))->qh_rlink = element->qh_rlink;
    ((struct quehead *)(element->qh_rlink))->qh_link = element->qh_link;
    element->qh_rlink = NULL;
}

int add_exec(struct ex_list **ex_ptr, int do_pty, char *exec,
             struct in_addr addr, int port)
{
    struct ex_list *tmp_ptr;

    /* First, check if the port is "bound" */
    for (tmp_ptr = *ex_ptr; tmp_ptr; tmp_ptr = tmp_ptr->ex_next) {
        if (port == tmp_ptr->ex_fport && addr.s_addr == tmp_ptr->ex_addr.s_addr)
            return -1;
    }

    tmp_ptr = *ex_ptr;
    *ex_ptr = g_new(struct ex_list, 1);
    (*ex_ptr)->ex_fport = port;
    (*ex_ptr)->ex_addr = addr;
    (*ex_ptr)->ex_pty = do_pty;
    (*ex_ptr)->ex_exec = (do_pty == 3) ? exec : g_strdup(exec);
    (*ex_ptr)->ex_next = tmp_ptr;
    return 0;
}


#ifdef _WIN32

int fork_exec(struct socket *so, const char *ex, int do_pty)
{
    /* not implemented */
    return 0;
}

#else

/*
 * XXX This is ugly
 * We create and bind a socket, then fork off to another
 * process, which connects to this socket, after which we
 * exec the wanted program.  If something (strange) happens,
 * the accept() call could block us forever.
 *
 * do_pty = 0   Fork/exec inetd style
 * do_pty = 1   Fork/exec using slirp.telnetd
 * do_ptr = 2   Fork/exec using pty
 */
int fork_exec(struct socket *so, const char *ex, int do_pty)
{
    int s, cs;
    struct sockaddr_in addr, csaddr;
    socklen_t addrlen = sizeof(addr);
    socklen_t csaddrlen = sizeof(csaddr);
    int opt;
    const char *argv[256];
    /* don't want to clobber the original */
    char *bptr;
    const char *curarg;
    int c, i, ret;
    pid_t pid;

    DEBUG_CALL("fork_exec");
    DEBUG_ARG("so = %p", so);
    DEBUG_ARG("ex = %p", ex);
    DEBUG_ARG("do_pty = %x", do_pty);

    if (do_pty == 2) {
        return 0;
    } else {
        addr.sin_family = AF_INET;
        addr.sin_port = 0;
        addr.sin_addr.s_addr = INADDR_ANY;

        if ((s = qemu_socket(AF_INET, SOCK_STREAM, 0)) < 0 ||
            bind(s, (struct sockaddr *)&addr, addrlen) < 0 ||
            listen(s, 1) < 0) {
            error_report("Error: inet socket: %s", strerror(errno));
            if (s >= 0) {
                closesocket(s);
            }

            return 0;
        }
    }

    if (getsockname(s, (struct sockaddr *)&csaddr, &csaddrlen) < 0) {
        closesocket(s);
        return 0;
    }
    cs = qemu_socket(AF_INET, SOCK_STREAM, 0);
    if (cs < 0) {
        closesocket(s);
        return 0;
    }
    csaddr.sin_addr = loopback_addr;
    /*
     * This connect won't block because we've already listen()ed on
     * the server end (even though we won't accept() the connection
     * until later on).
     */
    do {
        ret = connect(cs, (struct sockaddr *)&csaddr, csaddrlen);
    } while (ret < 0 && errno == EINTR);
    if (ret < 0) {
        closesocket(s);
        closesocket(cs);
        return 0;
    }

    pid = fork();
    switch (pid) {
    case -1:
        error_report("Error: fork failed: %s", strerror(errno));
        closesocket(cs);
        close(s);
        return 0;

    case 0:
        setsid();

        /* Set the DISPLAY */
        close(s);
        dup2(cs, 0);
        dup2(cs, 1);
        dup2(cs, 2);
        for (s = getdtablesize() - 1; s >= 3; s--)
            close(s);

        i = 0;
        bptr = g_strdup(ex); /* No need to free() this */
        if (do_pty == 1) {
            /* Setup "slirp.telnetd -x" */
            argv[i++] = "slirp.telnetd";
            argv[i++] = "-x";
            argv[i++] = bptr;
        } else
            do {
                /* Change the string into argv[] */
                curarg = bptr;
                while (*bptr != ' ' && *bptr != (char)0)
                    bptr++;
                c = *bptr;
                *bptr++ = (char)0;
                argv[i++] = g_strdup(curarg);
            } while (c);

        argv[i] = NULL;
        execvp(argv[0], (char **)argv);

        /* Ooops, failed, let's tell the user why */
        fprintf(stderr, "Error: execvp of %s failed: %s\n", argv[0],
                strerror(errno));
        close(0);
        close(1);
        close(2); /* XXX */
        exit(1);

    default:
        qemu_add_child_watch(pid);
        closesocket(cs);
        /*
         * This should never block, because we already connect()ed
         * on the child end before we forked.
         */
        do {
            so->s = accept(s, (struct sockaddr *)&addr, &addrlen);
        } while (so->s < 0 && errno == EINTR);
        closesocket(s);
        socket_set_fast_reuse(so->s);
        opt = 1;
        qemu_setsockopt(so->s, SOL_SOCKET, SO_OOBINLINE, &opt, sizeof(int));
        qemu_set_nonblock(so->s);

        /* Append the telnet options now */
        if (so->so_m != NULL && do_pty == 1) {
            sbappend(so, so->so_m);
            so->so_m = NULL;
        }

        return 1;
    }
}
#endif

void slirp_connection_info(Slirp *slirp, Monitor *mon)
{
    const char *const tcpstates[] = {
        [TCPS_CLOSED] = "CLOSED",           [TCPS_LISTEN] = "LISTEN",
        [TCPS_SYN_SENT] = "SYN_SENT",       [TCPS_SYN_RECEIVED] = "SYN_RCVD",
        [TCPS_ESTABLISHED] = "ESTABLISHED", [TCPS_CLOSE_WAIT] = "CLOSE_WAIT",
        [TCPS_FIN_WAIT_1] = "FIN_WAIT_1",   [TCPS_CLOSING] = "CLOSING",
        [TCPS_LAST_ACK] = "LAST_ACK",       [TCPS_FIN_WAIT_2] = "FIN_WAIT_2",
        [TCPS_TIME_WAIT] = "TIME_WAIT",
    };
    struct in_addr dst_addr;
    struct sockaddr_in src;
    socklen_t src_len;
    uint16_t dst_port;
    struct socket *so;
    const char *state;
    char buf[20];

    monitor_printf(mon, "  Protocol[State]    FD  Source Address  Port   "
                        "Dest. Address  Port RecvQ SendQ\n");

    for (so = slirp->tcb.so_next; so != &slirp->tcb; so = so->so_next) {
        if (so->so_state & SS_HOSTFWD) {
            state = "HOST_FORWARD";
        } else if (so->so_tcpcb) {
            state = tcpstates[so->so_tcpcb->t_state];
        } else {
            state = "NONE";
        }
        if (so->so_state & (SS_HOSTFWD | SS_INCOMING)) {
            src_len = sizeof(src);
            getsockname(so->s, (struct sockaddr *)&src, &src_len);
            dst_addr = so->so_laddr;
            dst_port = so->so_lport;
        } else {
            src.sin_addr = so->so_laddr;
            src.sin_port = so->so_lport;
            dst_addr = so->so_faddr;
            dst_port = so->so_fport;
        }
        snprintf(buf, sizeof(buf), "  TCP[%s]", state);
        monitor_printf(mon, "%-19s %3d %15s %5d ", buf, so->s,
                       src.sin_addr.s_addr ? inet_ntoa(src.sin_addr) : "*",
                       ntohs(src.sin_port));
        monitor_printf(mon, "%15s %5d %5d %5d\n", inet_ntoa(dst_addr),
                       ntohs(dst_port), so->so_rcv.sb_cc, so->so_snd.sb_cc);
    }

    for (so = slirp->udb.so_next; so != &slirp->udb; so = so->so_next) {
        if (so->so_state & SS_HOSTFWD) {
            snprintf(buf, sizeof(buf), "  UDP[HOST_FORWARD]");
            src_len = sizeof(src);
            getsockname(so->s, (struct sockaddr *)&src, &src_len);
            dst_addr = so->so_laddr;
            dst_port = so->so_lport;
        } else {
            snprintf(buf, sizeof(buf), "  UDP[%d sec]",
                     (so->so_expire - curtime) / 1000);
            src.sin_addr = so->so_laddr;
            src.sin_port = so->so_lport;
            dst_addr = so->so_faddr;
            dst_port = so->so_fport;
        }
        monitor_printf(mon, "%-19s %3d %15s %5d ", buf, so->s,
                       src.sin_addr.s_addr ? inet_ntoa(src.sin_addr) : "*",
                       ntohs(src.sin_port));
        monitor_printf(mon, "%15s %5d %5d %5d\n", inet_ntoa(dst_addr),
                       ntohs(dst_port), so->so_rcv.sb_cc, so->so_snd.sb_cc);
    }

    for (so = slirp->icmp.so_next; so != &slirp->icmp; so = so->so_next) {
        snprintf(buf, sizeof(buf), "  ICMP[%d sec]",
                 (so->so_expire - curtime) / 1000);
        src.sin_addr = so->so_laddr;
        dst_addr = so->so_faddr;
        monitor_printf(mon, "%-19s %3d %15s  -    ", buf, so->s,
                       src.sin_addr.s_addr ? inet_ntoa(src.sin_addr) : "*");
        monitor_printf(mon, "%15s  -    %5d %5d\n", inet_ntoa(dst_addr),
                       so->so_rcv.sb_cc, so->so_snd.sb_cc);
    }
}