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import of dnsmasq-2.33.tar.gz
This commit is contained in:
Simon Kelley
184
contrib/wrt/dhcp_release.c
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184
contrib/wrt/dhcp_release.c
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/* Copyright (c) 2006 Simon Kelley
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; version 2 dated June, 1991.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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*/
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/* dhcp_release <interface> <address> <MAC address> <client_id>
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MUST be run as root - will fail otherwise. */
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/* Send a DHCPRELEASE message via the specified interface
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to tell the local DHCP server to delete a particular lease.
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The interface argument is the interface in which a DHCP
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request _would_ be received if it was coming from the client,
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rather than being faked up here.
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The address argument is a dotted-quad IP addresses and mandatory.
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The MAC address is colon separated hex, and is mandatory. It may be
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prefixed by an address-type byte followed by -, eg
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10-11:22:33:44:55:66
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but if the address-type byte is missing it is assumed to be 1, the type
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for ethernet. This encoding is the one used in dnsmasq lease files.
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The client-id is optional. If it is "*" then it treated as being missing.
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*/
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#include <sys/types.h>
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#include <netinet/in.h>
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#include <net/if.h>
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#include <arpa/inet.h>
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#include <sys/socket.h>
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#include <unistd.h>
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#include <stdio.h>
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#include <string.h>
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#include <stdlib.h>
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#include <net/if_arp.h>
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#include <sys/ioctl.h>
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#define DHCP_CHADDR_MAX 16
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#define BOOTREQUEST 1
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#define DHCP_COOKIE 0x63825363
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#define OPTION_SERVER_IDENTIFIER 54
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#define OPTION_CLIENT_ID 61
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#define OPTION_MESSAGE_TYPE 53
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#define OPTION_END 255
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#define DHCPRELEASE 7
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#define DHCP_SERVER_PORT 67
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typedef unsigned char u8;
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typedef unsigned short u16;
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typedef unsigned int u32;
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struct dhcp_packet {
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u8 op, htype, hlen, hops;
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u32 xid;
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u16 secs, flags;
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struct in_addr ciaddr, yiaddr, siaddr, giaddr;
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u8 chaddr[DHCP_CHADDR_MAX], sname[64], file[128];
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u32 cookie;
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unsigned char options[308];
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};
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static int parse_hex(char *in, unsigned char *out, int maxlen, int *mac_type)
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{
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int i = 0;
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char *r;
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if (mac_type)
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*mac_type = 0;
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while (maxlen == -1 || i < maxlen)
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{
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for (r = in; *r != 0 && *r != ':' && *r != '-'; r++);
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if (*r == 0)
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maxlen = i;
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if (r != in )
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{
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if (*r == '-' && i == 0 && mac_type)
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{
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*r = 0;
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*mac_type = strtol(in, NULL, 16);
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mac_type = NULL;
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}
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else
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{
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*r = 0;
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out[i] = strtol(in, NULL, 16);
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i++;
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}
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}
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in = r+1;
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}
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return i;
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}
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int main(int argc, char **argv)
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{
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struct in_addr server, lease;
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int mac_type;
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struct dhcp_packet packet;
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unsigned char *p = packet.options;
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struct sockaddr_in dest;
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struct ifreq ifr;
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int fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP);
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if (argc < 4 || argc > 5)
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{
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fprintf(stderr, "usage: dhcp_release <interface> <addr> <mac> [<client_id>]\n");
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exit(1);
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}
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if (fd == -1)
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{
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perror("cannot create socket");
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exit(1);
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}
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/* This voodoo fakes up a packet coming from the correct interface, which really matters for
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a DHCP server */
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strcpy(ifr.ifr_name, argv[1]);
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ifr.ifr_addr.sa_family = AF_INET;
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if (ioctl(fd, SIOCGIFADDR, &ifr) == -1 || setsockopt(fd, SOL_SOCKET, SO_BINDTODEVICE, &ifr, sizeof(ifr)) == -1)
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{
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perror("cannot setup interface");
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exit(1);
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}
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server = ((struct sockaddr_in *) &ifr.ifr_addr)->sin_addr;
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lease.s_addr = inet_addr(argv[2]);
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memset(&packet, 0, sizeof(packet));
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packet.hlen = parse_hex(argv[3], packet.chaddr, DHCP_CHADDR_MAX, &mac_type);
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if (mac_type == 0)
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packet.htype = ARPHRD_ETHER;
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else
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packet.htype = mac_type;
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packet.op = BOOTREQUEST;
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packet.ciaddr = lease;
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packet.cookie = htonl(DHCP_COOKIE);
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*(p++) = OPTION_MESSAGE_TYPE;
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*(p++) = 1;
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*(p++) = DHCPRELEASE;
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*(p++) = OPTION_SERVER_IDENTIFIER;
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*(p++) = sizeof(server);
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memcpy(p, &server, sizeof(server));
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p += sizeof(server);
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if (argc == 5 && strcmp(argv[4], "*") != 0)
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{
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unsigned int clid_len = parse_hex(argv[4], p+2, 255, NULL);
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*(p++) = OPTION_CLIENT_ID;
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*(p++) = clid_len;
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p += clid_len;
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}
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*(p++) = OPTION_END;
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dest.sin_family = AF_INET;
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dest.sin_port = ntohs(DHCP_SERVER_PORT);
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dest.sin_addr = server;
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if (sendto(fd, &packet, sizeof(packet), 0,
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(struct sockaddr *)&dest, sizeof(dest)) == 1)
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{
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perror("sendto failed");
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exit(1);
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}
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return 0;
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}
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