udp.c

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/*
 * udp.c
 *
 * Copyright (c) 2001 Dug Song <dugsong@monkey.org>
 *
 * $Id: udp.c,v 1.8 2002/02/08 07:43:53 dugsong Exp $
 */

#include "config.h"

#include <sys/types.h>

#include <err.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>

#include "dnet.h"
#include "aton.h"
#include "mod.h"

void
udp_usage(void)
{
        fprintf(stderr, "Usage: dnet udp [sport|dport <value>] ...\n");
        exit(1);
}

int
udp_main(int argc, char *argv[])
{
        struct udp_hdr *udp;
        u_char *p, buf[IP_LEN_MAX];     /* XXX */
        char *name, *value;
        int c, len;

        srand(time(NULL));
        
        udp = (struct udp_hdr *)buf;
        
        memset(udp, 0, sizeof(*udp));
        udp->uh_sport = rand() & 0xffff;
        udp->uh_dport = rand() & 0xffff;
        
        for (c = 1; c + 1 < argc; c += 2) {
                name = argv[c];
                value = argv[c + 1];

                if (strcmp(name, "sport") == 0) {
                        if (port_aton(value, &udp->uh_sport) < 0)
                                udp_usage();
                } else if (strcmp(name, "dport") == 0) {
                        if (port_aton(value, &udp->uh_dport) < 0)
                                udp_usage();
                } else
                        udp_usage();
        }
        argc -= c;
        argv += c;

        if (argc != 0)
                udp_usage();

        p = buf + UDP_HDR_LEN;
        
        if (!isatty(STDIN_FILENO)) {
                len = sizeof(buf) - (p - buf);
                while ((c = read(STDIN_FILENO, p, len)) > 0) {
                        p += c;
                        len -= c;
                }
        }
        len = p - buf;
        udp->uh_ulen = htons(len);
        
        if (write(STDOUT_FILENO, buf, len) != len)
                err(1, "write");

        return (0);
}

struct mod mod_udp = {
        "udp",
        MOD_TYPE_ENCAP,
        udp_main
};

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