Simon Kelley | 5aabfc7 | 2007-08-29 11:24:47 +0100 | [diff] [blame] | 1 | /* Copyright (c) 2007 Simon Kelley |
| 2 | |
| 3 | This program is free software; you can redistribute it and/or modify |
| 4 | it under the terms of the GNU General Public License as published by |
| 5 | the Free Software Foundation; version 2 dated June, 1991. |
| 6 | |
| 7 | This program is distributed in the hope that it will be useful, |
| 8 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 9 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 10 | GNU General Public License for more details. |
| 11 | */ |
| 12 | |
| 13 | /* dhcp_lease_time <address> */ |
| 14 | |
| 15 | /* Send a DHCPINFORM message to a dnsmasq server running on the local host |
| 16 | and print (to stdout) the time remaining in any lease for the given |
| 17 | address. The time is given as string printed to stdout. |
| 18 | |
| 19 | If an error occurs or no lease exists for the given address, |
| 20 | nothing is sent to stdout a message is sent to stderr and a |
| 21 | non-zero error code is returned. |
| 22 | |
Simon Kelley | aa63a21 | 2013-04-22 15:01:52 +0100 | [diff] [blame] | 23 | This version requires dnsmasq 2.67 or later. |
Simon Kelley | 5aabfc7 | 2007-08-29 11:24:47 +0100 | [diff] [blame] | 24 | */ |
| 25 | |
| 26 | #include <sys/types.h> |
| 27 | #include <netinet/in.h> |
| 28 | #include <net/if.h> |
| 29 | #include <arpa/inet.h> |
| 30 | #include <sys/socket.h> |
| 31 | #include <unistd.h> |
| 32 | #include <stdio.h> |
| 33 | #include <string.h> |
| 34 | #include <stdlib.h> |
| 35 | #include <net/if_arp.h> |
| 36 | #include <sys/ioctl.h> |
| 37 | #include <linux/types.h> |
| 38 | #include <linux/netlink.h> |
| 39 | #include <linux/rtnetlink.h> |
| 40 | #include <errno.h> |
| 41 | |
| 42 | #define DHCP_CHADDR_MAX 16 |
| 43 | #define BOOTREQUEST 1 |
| 44 | #define DHCP_COOKIE 0x63825363 |
| 45 | #define OPTION_PAD 0 |
| 46 | #define OPTION_LEASE_TIME 51 |
| 47 | #define OPTION_OVERLOAD 52 |
| 48 | #define OPTION_MESSAGE_TYPE 53 |
Simon Kelley | aa63a21 | 2013-04-22 15:01:52 +0100 | [diff] [blame] | 49 | #define OPTION_REQUESTED_OPTIONS 55 |
Simon Kelley | 5aabfc7 | 2007-08-29 11:24:47 +0100 | [diff] [blame] | 50 | #define OPTION_END 255 |
| 51 | #define DHCPINFORM 8 |
| 52 | #define DHCP_SERVER_PORT 67 |
| 53 | |
| 54 | #define option_len(opt) ((int)(((unsigned char *)(opt))[1])) |
| 55 | #define option_ptr(opt) ((void *)&(((unsigned char *)(opt))[2])) |
| 56 | |
| 57 | |
| 58 | typedef unsigned char u8; |
| 59 | typedef unsigned short u16; |
| 60 | typedef unsigned int u32; |
| 61 | |
| 62 | struct dhcp_packet { |
| 63 | u8 op, htype, hlen, hops; |
| 64 | u32 xid; |
| 65 | u16 secs, flags; |
| 66 | struct in_addr ciaddr, yiaddr, siaddr, giaddr; |
| 67 | u8 chaddr[DHCP_CHADDR_MAX], sname[64], file[128]; |
| 68 | u32 cookie; |
| 69 | unsigned char options[308]; |
| 70 | }; |
| 71 | |
| 72 | static unsigned char *option_find1(unsigned char *p, unsigned char *end, int opt, int minsize) |
| 73 | { |
| 74 | while (*p != OPTION_END) |
| 75 | { |
| 76 | if (p >= end) |
| 77 | return NULL; /* malformed packet */ |
| 78 | else if (*p == OPTION_PAD) |
| 79 | p++; |
| 80 | else |
| 81 | { |
| 82 | int opt_len; |
| 83 | if (p >= end - 2) |
| 84 | return NULL; /* malformed packet */ |
| 85 | opt_len = option_len(p); |
Simon Kelley | 225accd | 2019-08-14 21:52:50 +0100 | [diff] [blame] | 86 | if (end - p < (2 + opt_len)) |
Simon Kelley | 5aabfc7 | 2007-08-29 11:24:47 +0100 | [diff] [blame] | 87 | return NULL; /* malformed packet */ |
| 88 | if (*p == opt && opt_len >= minsize) |
| 89 | return p; |
| 90 | p += opt_len + 2; |
| 91 | } |
| 92 | } |
| 93 | |
| 94 | return opt == OPTION_END ? p : NULL; |
| 95 | } |
| 96 | |
| 97 | static unsigned char *option_find(struct dhcp_packet *mess, size_t size, int opt_type, int minsize) |
| 98 | { |
| 99 | unsigned char *ret, *overload; |
| 100 | |
| 101 | /* skip over DHCP cookie; */ |
| 102 | if ((ret = option_find1(&mess->options[0], ((unsigned char *)mess) + size, opt_type, minsize))) |
| 103 | return ret; |
| 104 | |
| 105 | /* look for overload option. */ |
| 106 | if (!(overload = option_find1(&mess->options[0], ((unsigned char *)mess) + size, OPTION_OVERLOAD, 1))) |
| 107 | return NULL; |
| 108 | |
| 109 | /* Can we look in filename area ? */ |
| 110 | if ((overload[2] & 1) && |
| 111 | (ret = option_find1(&mess->file[0], &mess->file[128], opt_type, minsize))) |
| 112 | return ret; |
| 113 | |
| 114 | /* finally try sname area */ |
| 115 | if ((overload[2] & 2) && |
| 116 | (ret = option_find1(&mess->sname[0], &mess->sname[64], opt_type, minsize))) |
| 117 | return ret; |
| 118 | |
| 119 | return NULL; |
| 120 | } |
| 121 | |
| 122 | static unsigned int option_uint(unsigned char *opt, int size) |
| 123 | { |
| 124 | /* this worries about unaligned data and byte order */ |
| 125 | unsigned int ret = 0; |
| 126 | int i; |
| 127 | unsigned char *p = option_ptr(opt); |
| 128 | |
| 129 | for (i = 0; i < size; i++) |
| 130 | ret = (ret << 8) | *p++; |
| 131 | |
| 132 | return ret; |
| 133 | } |
| 134 | |
| 135 | int main(int argc, char **argv) |
| 136 | { |
| 137 | struct in_addr lease; |
| 138 | struct dhcp_packet packet; |
| 139 | unsigned char *p = packet.options; |
| 140 | struct sockaddr_in dest; |
| 141 | int fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP); |
| 142 | ssize_t rc; |
| 143 | |
| 144 | if (argc < 2) |
| 145 | { |
| 146 | fprintf(stderr, "usage: dhcp_lease_time <address>\n"); |
| 147 | exit(1); |
| 148 | } |
| 149 | |
| 150 | if (fd == -1) |
| 151 | { |
| 152 | perror("cannot create socket"); |
| 153 | exit(1); |
| 154 | } |
| 155 | |
| 156 | lease.s_addr = inet_addr(argv[1]); |
| 157 | |
| 158 | memset(&packet, 0, sizeof(packet)); |
| 159 | |
| 160 | packet.hlen = 0; |
| 161 | packet.htype = 0; |
| 162 | |
| 163 | packet.op = BOOTREQUEST; |
| 164 | packet.ciaddr = lease; |
| 165 | packet.cookie = htonl(DHCP_COOKIE); |
| 166 | |
| 167 | *(p++) = OPTION_MESSAGE_TYPE; |
| 168 | *(p++) = 1; |
| 169 | *(p++) = DHCPINFORM; |
| 170 | |
Josh Soref | 730c674 | 2017-02-06 16:14:04 +0000 | [diff] [blame] | 171 | /* Explicitly request the lease time, it won't be sent otherwise: |
Simon Kelley | aa63a21 | 2013-04-22 15:01:52 +0100 | [diff] [blame] | 172 | this is a dnsmasq extension, not standard. */ |
| 173 | *(p++) = OPTION_REQUESTED_OPTIONS; |
| 174 | *(p++) = 1; |
| 175 | *(p++) = OPTION_LEASE_TIME; |
| 176 | |
Simon Kelley | 5aabfc7 | 2007-08-29 11:24:47 +0100 | [diff] [blame] | 177 | *(p++) = OPTION_END; |
| 178 | |
| 179 | dest.sin_family = AF_INET; |
| 180 | dest.sin_addr.s_addr = inet_addr("127.0.0.1"); |
| 181 | dest.sin_port = ntohs(DHCP_SERVER_PORT); |
| 182 | |
| 183 | if (sendto(fd, &packet, sizeof(packet), 0, |
| 184 | (struct sockaddr *)&dest, sizeof(dest)) == -1) |
| 185 | { |
| 186 | perror("sendto failed"); |
| 187 | exit(1); |
| 188 | } |
| 189 | |
| 190 | alarm(3); /* noddy timeout. */ |
| 191 | |
| 192 | rc = recv(fd, &packet, sizeof(packet), 0); |
| 193 | |
| 194 | if (rc < (ssize_t)(sizeof(packet) - sizeof(packet.options))) |
| 195 | { |
| 196 | perror("recv failed"); |
| 197 | exit(1); |
| 198 | } |
| 199 | |
| 200 | if ((p = option_find(&packet, (size_t)rc, OPTION_LEASE_TIME, 4))) |
| 201 | { |
| 202 | unsigned int t = option_uint(p, 4); |
| 203 | if (t == 0xffffffff) |
| 204 | printf("infinite"); |
| 205 | else |
| 206 | { |
| 207 | unsigned int x; |
| 208 | if ((x = t/86400)) |
Rosen Penev | cbd29e5 | 2017-06-27 22:29:51 +0100 | [diff] [blame] | 209 | printf("%ud", x); |
Simon Kelley | 5aabfc7 | 2007-08-29 11:24:47 +0100 | [diff] [blame] | 210 | if ((x = (t/3600)%24)) |
Rosen Penev | cbd29e5 | 2017-06-27 22:29:51 +0100 | [diff] [blame] | 211 | printf("%uh", x); |
Simon Kelley | 5aabfc7 | 2007-08-29 11:24:47 +0100 | [diff] [blame] | 212 | if ((x = (t/60)%60)) |
Rosen Penev | cbd29e5 | 2017-06-27 22:29:51 +0100 | [diff] [blame] | 213 | printf("%um", x); |
Simon Kelley | 5aabfc7 | 2007-08-29 11:24:47 +0100 | [diff] [blame] | 214 | if ((x = t%60)) |
Rosen Penev | cbd29e5 | 2017-06-27 22:29:51 +0100 | [diff] [blame] | 215 | printf("%us", x); |
Simon Kelley | 5aabfc7 | 2007-08-29 11:24:47 +0100 | [diff] [blame] | 216 | } |
| 217 | return 0; |
| 218 | } |
| 219 | |
| 220 | return 1; /* no lease */ |
| 221 | } |