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Diffstat (limited to 'contrib/wrt/dhcp_lease_time.c')
| -rwxr-xr-x | contrib/wrt/dhcp_lease_time.c | 214 |
1 files changed, 214 insertions, 0 deletions
diff --git a/contrib/wrt/dhcp_lease_time.c b/contrib/wrt/dhcp_lease_time.c new file mode 100755 index 0000000..2866bb5 --- /dev/null +++ b/contrib/wrt/dhcp_lease_time.c @@ -0,0 +1,214 @@ +/* Copyright (c) 2007 Simon Kelley + + 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; version 2 dated June, 1991. + + 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. +*/ + +/* dhcp_lease_time <address> */ + +/* Send a DHCPINFORM message to a dnsmasq server running on the local host + and print (to stdout) the time remaining in any lease for the given + address. The time is given as string printed to stdout. + + If an error occurs or no lease exists for the given address, + nothing is sent to stdout a message is sent to stderr and a + non-zero error code is returned. + + Requires dnsmasq 2.40 or later. +*/ + +#include <sys/types.h> +#include <netinet/in.h> +#include <net/if.h> +#include <arpa/inet.h> +#include <sys/socket.h> +#include <unistd.h> +#include <stdio.h> +#include <string.h> +#include <stdlib.h> +#include <net/if_arp.h> +#include <sys/ioctl.h> +#include <linux/types.h> +#include <linux/netlink.h> +#include <linux/rtnetlink.h> +#include <errno.h> + +#define DHCP_CHADDR_MAX 16 +#define BOOTREQUEST 1 +#define DHCP_COOKIE 0x63825363 +#define OPTION_PAD 0 +#define OPTION_LEASE_TIME 51 +#define OPTION_OVERLOAD 52 +#define OPTION_MESSAGE_TYPE 53 +#define OPTION_END 255 +#define DHCPINFORM 8 +#define DHCP_SERVER_PORT 67 + +#define option_len(opt) ((int)(((unsigned char *)(opt))[1])) +#define option_ptr(opt) ((void *)&(((unsigned char *)(opt))[2])) + + +typedef unsigned char u8; +typedef unsigned short u16; +typedef unsigned int u32; + +struct dhcp_packet { + u8 op, htype, hlen, hops; + u32 xid; + u16 secs, flags; + struct in_addr ciaddr, yiaddr, siaddr, giaddr; + u8 chaddr[DHCP_CHADDR_MAX], sname[64], file[128]; + u32 cookie; + unsigned char options[308]; +}; + +static unsigned char *option_find1(unsigned char *p, unsigned char *end, int opt, int minsize) +{ + while (*p != OPTION_END) + { + if (p >= end) + return NULL; /* malformed packet */ + else if (*p == OPTION_PAD) + p++; + else + { + int opt_len; + if (p >= end - 2) + return NULL; /* malformed packet */ + opt_len = option_len(p); + if (p >= end - (2 + opt_len)) + return NULL; /* malformed packet */ + if (*p == opt && opt_len >= minsize) + return p; + p += opt_len + 2; + } + } + + return opt == OPTION_END ? p : NULL; +} + +static unsigned char *option_find(struct dhcp_packet *mess, size_t size, int opt_type, int minsize) +{ + unsigned char *ret, *overload; + + /* skip over DHCP cookie; */ + if ((ret = option_find1(&mess->options[0], ((unsigned char *)mess) + size, opt_type, minsize))) + return ret; + + /* look for overload option. */ + if (!(overload = option_find1(&mess->options[0], ((unsigned char *)mess) + size, OPTION_OVERLOAD, 1))) + return NULL; + + /* Can we look in filename area ? */ + if ((overload[2] & 1) && + (ret = option_find1(&mess->file[0], &mess->file[128], opt_type, minsize))) + return ret; + + /* finally try sname area */ + if ((overload[2] & 2) && + (ret = option_find1(&mess->sname[0], &mess->sname[64], opt_type, minsize))) + return ret; + + return NULL; +} + +static unsigned int option_uint(unsigned char *opt, int size) +{ + /* this worries about unaligned data and byte order */ + unsigned int ret = 0; + int i; + unsigned char *p = option_ptr(opt); + + for (i = 0; i < size; i++) + ret = (ret << 8) | *p++; + + return ret; +} + +int main(int argc, char **argv) +{ + struct in_addr lease; + struct dhcp_packet packet; + unsigned char *p = packet.options; + struct sockaddr_in dest; + int fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP); + ssize_t rc; + + if (argc < 2) + { + fprintf(stderr, "usage: dhcp_lease_time <address>\n"); + exit(1); + } + + if (fd == -1) + { + perror("cannot create socket"); + exit(1); + } + + lease.s_addr = inet_addr(argv[1]); + + memset(&packet, 0, sizeof(packet)); + + packet.hlen = 0; + packet.htype = 0; + + packet.op = BOOTREQUEST; + packet.ciaddr = lease; + packet.cookie = htonl(DHCP_COOKIE); + + *(p++) = OPTION_MESSAGE_TYPE; + *(p++) = 1; + *(p++) = DHCPINFORM; + + *(p++) = OPTION_END; + + dest.sin_family = AF_INET; + dest.sin_addr.s_addr = inet_addr("127.0.0.1"); + dest.sin_port = ntohs(DHCP_SERVER_PORT); + + if (sendto(fd, &packet, sizeof(packet), 0, + (struct sockaddr *)&dest, sizeof(dest)) == -1) + { + perror("sendto failed"); + exit(1); + } + + alarm(3); /* noddy timeout. */ + + rc = recv(fd, &packet, sizeof(packet), 0); + + if (rc < (ssize_t)(sizeof(packet) - sizeof(packet.options))) + { + perror("recv failed"); + exit(1); + } + + if ((p = option_find(&packet, (size_t)rc, OPTION_LEASE_TIME, 4))) + { + unsigned int t = option_uint(p, 4); + if (t == 0xffffffff) + printf("infinite"); + else + { + unsigned int x; + if ((x = t/86400)) + printf("%dd", x); + if ((x = (t/3600)%24)) + printf("%dh", x); + if ((x = (t/60)%60)) + printf("%dm", x); + if ((x = t%60)) + printf("%ds", x); + } + return 0; + } + + return 1; /* no lease */ +} |