libnetutils/dhcpclient.c - platform/system/core - Gitiles

 /*
  * Copyright 2008, The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *     http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 #include <stdio.h>
 #include <stdarg.h>
 #include <stdlib.h>
 #include <unistd.h>
 #include <errno.h>
 #include <string.h>

 #include <time.h>
 #include <sys/time.h>
 #include <poll.h>

 #include <sys/socket.h>
 #include <sys/select.h>
 #include <sys/types.h>
 #include <netinet/in.h>

 #include <cutils/properties.h>
 #define LOG_TAG "DHCP"
 #include <cutils/log.h>

 #include <dirent.h>

 #include <netutils/ifc.h>
 #include "dhcpmsg.h"
 #include "packet.h"

 #define VERBOSE 2

 static int verbose = 1;
 static char errmsg[2048];

 typedef unsigned long long msecs_t;
 #if VERBOSE
 void dump_dhcp_msg();
 #endif

 msecs_t get_msecs(void)
 {
     struct timespec ts;

     if (clock_gettime(CLOCK_MONOTONIC, &ts)) {
         return 0;
     } else {
         return (((msecs_t) ts.tv_sec) * ((msecs_t) 1000)) +
             (((msecs_t) ts.tv_nsec) / ((msecs_t) 1000000));
     }
 }

 void printerr(char *fmt, ...)
 {
     va_list ap;

     va_start(ap, fmt);
     vsnprintf(errmsg, sizeof(errmsg), fmt, ap);
     va_end(ap);

     LOGD("%s", errmsg);
 }

 const char *dhcp_lasterror()
 {
     return errmsg;
 }

 int fatal(const char *reason)
 {
     printerr("%s: %s\n", reason, strerror(errno));
     return -1;
 //    exit(1);
 }

 const char *ipaddr(in_addr_t addr)
 {
     struct in_addr in_addr;

     in_addr.s_addr = addr;
     return inet_ntoa(in_addr);
 }

 extern int ipv4NetmaskToPrefixLength(in_addr_t mask);

 typedef struct dhcp_info dhcp_info;

 struct dhcp_info {
     uint32_t type;

     uint32_t ipaddr;
     uint32_t gateway;
     uint32_t prefixLength;

     uint32_t dns1;
     uint32_t dns2;

     uint32_t serveraddr;
     uint32_t lease;
 };

 dhcp_info last_good_info;

 void get_dhcp_info(uint32_t *ipaddr, uint32_t *gateway, uint32_t *prefixLength,
                    uint32_t *dns1, uint32_t *dns2, uint32_t *server,
                    uint32_t *lease)
 {
     *ipaddr = last_good_info.ipaddr;
     *gateway = last_good_info.gateway;
     *prefixLength = last_good_info.prefixLength;
     *dns1 = last_good_info.dns1;
     *dns2 = last_good_info.dns2;
     *server = last_good_info.serveraddr;
     *lease = last_good_info.lease;
 }

 static int dhcp_configure(const char *ifname, dhcp_info *info)
 {
     last_good_info = *info;
     return ifc_configure(ifname, info->ipaddr, info->prefixLength, info->gateway,
                          info->dns1, info->dns2);
 }

 static const char *dhcp_type_to_name(uint32_t type)
 {
     switch(type) {
     case DHCPDISCOVER: return "discover";
     case DHCPOFFER:    return "offer";
     case DHCPREQUEST:  return "request";
     case DHCPDECLINE:  return "decline";
     case DHCPACK:      return "ack";
     case DHCPNAK:      return "nak";
     case DHCPRELEASE:  return "release";
     case DHCPINFORM:   return "inform";
     default:           return "???";
     }
 }

 void dump_dhcp_info(dhcp_info *info)
 {
     char addr[20], gway[20], mask[20];
     LOGD("--- dhcp %s (%d) ---",
             dhcp_type_to_name(info->type), info->type);
     strcpy(addr, ipaddr(info->ipaddr));
     strcpy(gway, ipaddr(info->gateway));
     LOGD("ip %s gw %s prefixLength %d", addr, gway, info->prefixLength);
     if (info->dns1) LOGD("dns1: %s", ipaddr(info->dns1));
     if (info->dns2) LOGD("dns2: %s", ipaddr(info->dns2));
     LOGD("server %s, lease %d seconds",
             ipaddr(info->serveraddr), info->lease);
 }


 int decode_dhcp_msg(dhcp_msg *msg, int len, dhcp_info *info)
 {
     uint8_t *x;
     unsigned int opt;
     int optlen;

     memset(info, 0, sizeof(dhcp_info));
     if (len < (DHCP_MSG_FIXED_SIZE + 4)) return -1;

     len -= (DHCP_MSG_FIXED_SIZE + 4);

     if (msg->options[0] != OPT_COOKIE1) return -1;
     if (msg->options[1] != OPT_COOKIE2) return -1;
     if (msg->options[2] != OPT_COOKIE3) return -1;
     if (msg->options[3] != OPT_COOKIE4) return -1;

     x = msg->options + 4;

     while (len > 2) {
         opt = *x++;
         if (opt == OPT_PAD) {
             len--;
             continue;
         }
         if (opt == OPT_END) {
             break;
         }
         optlen = *x++;
         len -= 2;
         if (optlen > len) {
             break;
         }
         switch(opt) {
         case OPT_SUBNET_MASK:
             if (optlen >= 4) info->prefixLength = ipv4NetmaskToPrefixLength((int)x);
             break;
         case OPT_GATEWAY:
             if (optlen >= 4) memcpy(&info->gateway, x, 4);
             break;
         case OPT_DNS:
             if (optlen >= 4) memcpy(&info->dns1, x + 0, 4);
             if (optlen >= 8) memcpy(&info->dns2, x + 4, 4);
             break;
         case OPT_LEASE_TIME:
             if (optlen >= 4) {
                 memcpy(&info->lease, x, 4);
                 info->lease = ntohl(info->lease);
             }
             break;
         case OPT_SERVER_ID:
             if (optlen >= 4) memcpy(&info->serveraddr, x, 4);
             break;
         case OPT_MESSAGE_TYPE:
             info->type = *x;
             break;
         default:
             break;
         }
         x += optlen;
         len -= optlen;
     }

     info->ipaddr = msg->yiaddr;

     return 0;
 }

 #if VERBOSE

 static void hex2str(char *buf, const unsigned char *array, int len)
 {
     int i;
     char *cp = buf;

     for (i = 0; i < len; i++) {
         cp += sprintf(cp, " %02x ", array[i]);
     }
 }

 void dump_dhcp_msg(dhcp_msg *msg, int len)
 {
     unsigned char *x;
     unsigned int n,c;
     int optsz;
     const char *name;
     char buf[2048];

     LOGD("===== DHCP message:");
     if (len < DHCP_MSG_FIXED_SIZE) {
         LOGD("Invalid length %d, should be %d", len, DHCP_MSG_FIXED_SIZE);
         return;
     }

     len -= DHCP_MSG_FIXED_SIZE;

     if (msg->op == OP_BOOTREQUEST)
         name = "BOOTREQUEST";
     else if (msg->op == OP_BOOTREPLY)
         name = "BOOTREPLY";
     else
         name = "????";
     LOGD("op = %s (%d), htype = %d, hlen = %d, hops = %d",
            name, msg->op, msg->htype, msg->hlen, msg->hops);
     LOGD("xid = 0x%08x secs = %d, flags = 0x%04x optlen = %d",
            ntohl(msg->xid), ntohs(msg->secs), ntohs(msg->flags), len);
     LOGD("ciaddr = %s", ipaddr(msg->ciaddr));
     LOGD("yiaddr = %s", ipaddr(msg->yiaddr));
     LOGD("siaddr = %s", ipaddr(msg->siaddr));
     LOGD("giaddr = %s", ipaddr(msg->giaddr));

     c = msg->hlen > 16 ? 16 : msg->hlen;
     hex2str(buf, msg->chaddr, c);
     LOGD("chaddr = {%s}", buf);

     for (n = 0; n < 64; n++) {
         if ((msg->sname[n] < ' ') || (msg->sname[n] > 127)) {
             if (msg->sname[n] == 0) break;
             msg->sname[n] = '.';
         }
     }
     msg->sname[63] = 0;

     for (n = 0; n < 128; n++) {
         if ((msg->file[n] < ' ') || (msg->file[n] > 127)) {
             if (msg->file[n] == 0) break;
             msg->file[n] = '.';
         }
     }
     msg->file[127] = 0;

     LOGD("sname = '%s'", msg->sname);
     LOGD("file = '%s'", msg->file);

     if (len < 4) return;
     len -= 4;
     x = msg->options + 4;

     while (len > 2) {
         if (*x == 0) {
             x++;
             len--;
             continue;
         }
         if (*x == OPT_END) {
             break;
         }
         len -= 2;
         optsz = x[1];
         if (optsz > len) break;
         if (x[0] == OPT_DOMAIN_NAME || x[0] == OPT_MESSAGE) {
             if ((unsigned int)optsz < sizeof(buf) - 1) {
                 n = optsz;
             } else {
                 n = sizeof(buf) - 1;
             }
             memcpy(buf, &x[2], n);
             buf[n] = '\0';
         } else {
             hex2str(buf, &x[2], optsz);
         }
         if (x[0] == OPT_MESSAGE_TYPE)
             name = dhcp_type_to_name(x[2]);
         else
             name = NULL;
         LOGD("op %d len %d {%s} %s", x[0], optsz, buf, name == NULL ? "" : name);
         len -= optsz;
         x = x + optsz + 2;
     }
 }

 #endif

 static int send_message(int sock, int if_index, dhcp_msg  *msg, int size)
 {
 #if VERBOSE > 1
     dump_dhcp_msg(msg, size);
 #endif
     return send_packet(sock, if_index, msg, size, INADDR_ANY, INADDR_BROADCAST,
                        PORT_BOOTP_CLIENT, PORT_BOOTP_SERVER);
 }

 static int is_valid_reply(dhcp_msg *msg, dhcp_msg *reply, int sz)
 {
     if (sz < DHCP_MSG_FIXED_SIZE) {
         if (verbose) LOGD("netcfg: Wrong size %d != %d\n", sz, DHCP_MSG_FIXED_SIZE);
         return 0;
     }
     if (reply->op != OP_BOOTREPLY) {
         if (verbose) LOGD("netcfg: Wrong Op %d != %d\n", reply->op, OP_BOOTREPLY);
         return 0;
     }
     if (reply->xid != msg->xid) {
         if (verbose) LOGD("netcfg: Wrong Xid 0x%x != 0x%x\n", ntohl(reply->xid),
                           ntohl(msg->xid));
         return 0;
     }
     if (reply->htype != msg->htype) {
         if (verbose) LOGD("netcfg: Wrong Htype %d != %d\n", reply->htype, msg->htype);
         return 0;
     }
     if (reply->hlen != msg->hlen) {
         if (verbose) LOGD("netcfg: Wrong Hlen %d != %d\n", reply->hlen, msg->hlen);
         return 0;
     }
     if (memcmp(msg->chaddr, reply->chaddr, msg->hlen)) {
         if (verbose) LOGD("netcfg: Wrong chaddr %x != %x\n", *(reply->chaddr),*(msg->chaddr));
         return 0;
     }
     return 1;
 }

 #define STATE_SELECTING  1
 #define STATE_REQUESTING 2

 #define TIMEOUT_INITIAL   4000
 #define TIMEOUT_MAX      32000

 int dhcp_init_ifc(const char *ifname)
 {
     dhcp_msg discover_msg;
     dhcp_msg request_msg;
     dhcp_msg reply;
     dhcp_msg *msg;
     dhcp_info info;
     int s, r, size;
     int valid_reply;
     uint32_t xid;
     unsigned char hwaddr[6];
     struct pollfd pfd;
     unsigned int state;
     unsigned int timeout;
     int if_index;

     xid = (uint32_t) get_msecs();

     if (ifc_get_hwaddr(ifname, hwaddr)) {
         return fatal("cannot obtain interface address");
     }
     if (ifc_get_ifindex(ifname, &if_index)) {
         return fatal("cannot obtain interface index");
     }

     s = open_raw_socket(ifname, hwaddr, if_index);

     timeout = TIMEOUT_INITIAL;
     state = STATE_SELECTING;
     info.type = 0;
     goto transmit;

     for (;;) {
         pfd.fd = s;
         pfd.events = POLLIN;
         pfd.revents = 0;
         r = poll(&pfd, 1, timeout);

         if (r == 0) {
 #if VERBOSE
             printerr("TIMEOUT\n");
 #endif
             if (timeout >= TIMEOUT_MAX) {
                 printerr("timed out\n");
                 if ( info.type == DHCPOFFER ) {
                     printerr("no acknowledgement from DHCP server\nconfiguring %s with offered parameters\n", ifname);
                     return dhcp_configure(ifname, &info);
                 }
                 errno = ETIME;
                 close(s);
                 return -1;
             }
             timeout = timeout * 2;

         transmit:
             size = 0;
             msg = NULL;
             switch(state) {
             case STATE_SELECTING:
                 msg = &discover_msg;
                 size = init_dhcp_discover_msg(msg, hwaddr, xid);
                 break;
             case STATE_REQUESTING:
                 msg = &request_msg;
                 size = init_dhcp_request_msg(msg, hwaddr, xid, info.ipaddr, info.serveraddr);
                 break;
             default:
                 r = 0;
             }
             if (size != 0) {
                 r = send_message(s, if_index, msg, size);
                 if (r < 0) {
                     printerr("error sending dhcp msg: %s\n", strerror(errno));
                 }
             }
             continue;
         }

         if (r < 0) {
             if ((errno == EAGAIN) || (errno == EINTR)) {
                 continue;
             }
             return fatal("poll failed");
         }

         errno = 0;
         r = receive_packet(s, &reply);
         if (r < 0) {
             if (errno != 0) {
                 LOGD("receive_packet failed (%d): %s", r, strerror(errno));
                 if (errno == ENETDOWN || errno == ENXIO) {
                     return -1;
                 }
             }
             continue;
         }

 #if VERBOSE > 1
         dump_dhcp_msg(&reply, r);
 #endif
         decode_dhcp_msg(&reply, r, &info);

         if (state == STATE_SELECTING) {
             valid_reply = is_valid_reply(&discover_msg, &reply, r);
         } else {
             valid_reply = is_valid_reply(&request_msg, &reply, r);
         }
         if (!valid_reply) {
             printerr("invalid reply\n");
             continue;
         }

         if (verbose) dump_dhcp_info(&info);

         switch(state) {
         case STATE_SELECTING:
             if (info.type == DHCPOFFER) {
                 state = STATE_REQUESTING;
                 timeout = TIMEOUT_INITIAL;
                 xid++;
                 goto transmit;
             }
             break;
         case STATE_REQUESTING:
             if (info.type == DHCPACK) {
                 printerr("configuring %s\n", ifname);
                 close(s);
                 return dhcp_configure(ifname, &info);
             } else if (info.type == DHCPNAK) {
                 printerr("configuration request denied\n");
                 close(s);
                 return -1;
             } else {
                 printerr("ignoring %s message in state %d\n",
                          dhcp_type_to_name(info.type), state);
             }
             break;
         }
     }
     close(s);
     return 0;
 }

 int do_dhcp(char *iname)
 {
     if (ifc_set_addr(iname, 0)) {
         printerr("failed to set ip addr for %s to 0.0.0.0: %s\n", iname, strerror(errno));
         return -1;
     }

     if (ifc_up(iname)) {
         printerr("failed to bring up interface %s: %s\n", iname, strerror(errno));
         return -1;
     }

     return dhcp_init_ifc(iname);
 }
	/*
	* Copyright 2008, The Android Open Source Project
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	#include <stdio.h>
	#include <stdarg.h>
	#include <stdlib.h>
	#include <unistd.h>
	#include <errno.h>
	#include <string.h>

	#include <time.h>
	#include <sys/time.h>
	#include <poll.h>

	#include <sys/socket.h>
	#include <sys/select.h>
	#include <sys/types.h>
	#include <netinet/in.h>

	#include <cutils/properties.h>
	#define LOG_TAG "DHCP"
	#include <cutils/log.h>

	#include <dirent.h>

	#include <netutils/ifc.h>
	#include "dhcpmsg.h"
	#include "packet.h"

	#define VERBOSE 2

	static int verbose = 1;
	static char errmsg[2048];

	typedef unsigned long long msecs_t;
	#if VERBOSE
	void dump_dhcp_msg();
	#endif

	msecs_t get_msecs(void)
	{
	struct timespec ts;

	if (clock_gettime(CLOCK_MONOTONIC, &ts)) {
	return 0;
	} else {
	return (((msecs_t) ts.tv_sec) * ((msecs_t) 1000)) +
	(((msecs_t) ts.tv_nsec) / ((msecs_t) 1000000));
	}
	}

	void printerr(char *fmt, ...)
	{
	va_list ap;

	va_start(ap, fmt);
	vsnprintf(errmsg, sizeof(errmsg), fmt, ap);
	va_end(ap);

	LOGD("%s", errmsg);
	}

	const char *dhcp_lasterror()
	{
	return errmsg;
	}

	int fatal(const char *reason)
	{
	printerr("%s: %s\n", reason, strerror(errno));
	return -1;
	// exit(1);
	}

	const char *ipaddr(in_addr_t addr)
	{
	struct in_addr in_addr;

	in_addr.s_addr = addr;
	return inet_ntoa(in_addr);
	}

	extern int ipv4NetmaskToPrefixLength(in_addr_t mask);

	typedef struct dhcp_info dhcp_info;

	struct dhcp_info {
	uint32_t type;

	uint32_t ipaddr;
	uint32_t gateway;
	uint32_t prefixLength;

	uint32_t dns1;
	uint32_t dns2;

	uint32_t serveraddr;
	uint32_t lease;
	};

	dhcp_info last_good_info;

	void get_dhcp_info(uint32_t ipaddr, uint32_t gateway, uint32_t *prefixLength,
	uint32_t dns1, uint32_t dns2, uint32_t *server,
	uint32_t *lease)
	{
	*ipaddr = last_good_info.ipaddr;
	*gateway = last_good_info.gateway;
	*prefixLength = last_good_info.prefixLength;
	*dns1 = last_good_info.dns1;
	*dns2 = last_good_info.dns2;
	*server = last_good_info.serveraddr;
	*lease = last_good_info.lease;
	}

	static int dhcp_configure(const char ifname, dhcp_info info)
	{
	last_good_info = *info;
	return ifc_configure(ifname, info->ipaddr, info->prefixLength, info->gateway,
	info->dns1, info->dns2);
	}

	static const char *dhcp_type_to_name(uint32_t type)
	{
	switch(type) {
	case DHCPDISCOVER: return "discover";
	case DHCPOFFER: return "offer";
	case DHCPREQUEST: return "request";
	case DHCPDECLINE: return "decline";
	case DHCPACK: return "ack";
	case DHCPNAK: return "nak";
	case DHCPRELEASE: return "release";
	case DHCPINFORM: return "inform";
	default: return "???";
	}
	}

	void dump_dhcp_info(dhcp_info *info)
	{
	char addr[20], gway[20], mask[20];
	LOGD("--- dhcp %s (%d) ---",
	dhcp_type_to_name(info->type), info->type);
	strcpy(addr, ipaddr(info->ipaddr));
	strcpy(gway, ipaddr(info->gateway));
	LOGD("ip %s gw %s prefixLength %d", addr, gway, info->prefixLength);
	if (info->dns1) LOGD("dns1: %s", ipaddr(info->dns1));
	if (info->dns2) LOGD("dns2: %s", ipaddr(info->dns2));
	LOGD("server %s, lease %d seconds",
	ipaddr(info->serveraddr), info->lease);
	}


	int decode_dhcp_msg(dhcp_msg msg, int len, dhcp_info info)
	{
	uint8_t *x;
	unsigned int opt;
	int optlen;

	memset(info, 0, sizeof(dhcp_info));
	if (len < (DHCP_MSG_FIXED_SIZE + 4)) return -1;

	len -= (DHCP_MSG_FIXED_SIZE + 4);

	if (msg->options[0] != OPT_COOKIE1) return -1;
	if (msg->options[1] != OPT_COOKIE2) return -1;
	if (msg->options[2] != OPT_COOKIE3) return -1;
	if (msg->options[3] != OPT_COOKIE4) return -1;

	x = msg->options + 4;

	while (len > 2) {
	opt = *x++;
	if (opt == OPT_PAD) {
	len--;
	continue;
	}
	if (opt == OPT_END) {
	break;
	}
	optlen = *x++;
	len -= 2;
	if (optlen > len) {
	break;
	}
	switch(opt) {
	case OPT_SUBNET_MASK:
	if (optlen >= 4) info->prefixLength = ipv4NetmaskToPrefixLength((int)x);
	break;
	case OPT_GATEWAY:
	if (optlen >= 4) memcpy(&info->gateway, x, 4);
	break;
	case OPT_DNS:
	if (optlen >= 4) memcpy(&info->dns1, x + 0, 4);
	if (optlen >= 8) memcpy(&info->dns2, x + 4, 4);
	break;
	case OPT_LEASE_TIME:
	if (optlen >= 4) {
	memcpy(&info->lease, x, 4);
	info->lease = ntohl(info->lease);
	}
	break;
	case OPT_SERVER_ID:
	if (optlen >= 4) memcpy(&info->serveraddr, x, 4);
	break;
	case OPT_MESSAGE_TYPE:
	info->type = *x;
	break;
	default:
	break;
	}
	x += optlen;
	len -= optlen;
	}

	info->ipaddr = msg->yiaddr;

	return 0;
	}

	#if VERBOSE

	static void hex2str(char buf, const unsigned char array, int len)
	{
	int i;
	char *cp = buf;

	for (i = 0; i < len; i++) {
	cp += sprintf(cp, " %02x ", array[i]);
	}
	}

	void dump_dhcp_msg(dhcp_msg *msg, int len)
	{
	unsigned char *x;
	unsigned int n,c;
	int optsz;
	const char *name;
	char buf[2048];

	LOGD("===== DHCP message:");
	if (len < DHCP_MSG_FIXED_SIZE) {
	LOGD("Invalid length %d, should be %d", len, DHCP_MSG_FIXED_SIZE);
	return;
	}

	len -= DHCP_MSG_FIXED_SIZE;

	if (msg->op == OP_BOOTREQUEST)
	name = "BOOTREQUEST";
	else if (msg->op == OP_BOOTREPLY)
	name = "BOOTREPLY";
	else
	name = "????";
	LOGD("op = %s (%d), htype = %d, hlen = %d, hops = %d",
	name, msg->op, msg->htype, msg->hlen, msg->hops);
	LOGD("xid = 0x%08x secs = %d, flags = 0x%04x optlen = %d",
	ntohl(msg->xid), ntohs(msg->secs), ntohs(msg->flags), len);
	LOGD("ciaddr = %s", ipaddr(msg->ciaddr));
	LOGD("yiaddr = %s", ipaddr(msg->yiaddr));
	LOGD("siaddr = %s", ipaddr(msg->siaddr));
	LOGD("giaddr = %s", ipaddr(msg->giaddr));

	c = msg->hlen > 16 ? 16 : msg->hlen;
	hex2str(buf, msg->chaddr, c);
	LOGD("chaddr = {%s}", buf);

	for (n = 0; n < 64; n++) {
	if ((msg->sname[n] < ' ') \|\| (msg->sname[n] > 127)) {
	if (msg->sname[n] == 0) break;
	msg->sname[n] = '.';
	}
	}
	msg->sname[63] = 0;

	for (n = 0; n < 128; n++) {
	if ((msg->file[n] < ' ') \|\| (msg->file[n] > 127)) {
	if (msg->file[n] == 0) break;
	msg->file[n] = '.';
	}
	}
	msg->file[127] = 0;

	LOGD("sname = '%s'", msg->sname);
	LOGD("file = '%s'", msg->file);

	if (len < 4) return;
	len -= 4;
	x = msg->options + 4;

	while (len > 2) {
	if (*x == 0) {
	x++;
	len--;
	continue;
	}
	if (*x == OPT_END) {
	break;
	}
	len -= 2;
	optsz = x[1];
	if (optsz > len) break;
	if (x[0] == OPT_DOMAIN_NAME \|\| x[0] == OPT_MESSAGE) {
	if ((unsigned int)optsz < sizeof(buf) - 1) {
	n = optsz;
	} else {
	n = sizeof(buf) - 1;
	}
	memcpy(buf, &x[2], n);
	buf[n] = '\0';
	} else {
	hex2str(buf, &x[2], optsz);
	}
	if (x[0] == OPT_MESSAGE_TYPE)
	name = dhcp_type_to_name(x[2]);
	else
	name = NULL;
	LOGD("op %d len %d {%s} %s", x[0], optsz, buf, name == NULL ? "" : name);
	len -= optsz;
	x = x + optsz + 2;
	}
	}

	#endif

	static int send_message(int sock, int if_index, dhcp_msg *msg, int size)
	{
	#if VERBOSE > 1
	dump_dhcp_msg(msg, size);
	#endif
	return send_packet(sock, if_index, msg, size, INADDR_ANY, INADDR_BROADCAST,
	PORT_BOOTP_CLIENT, PORT_BOOTP_SERVER);
	}

	static int is_valid_reply(dhcp_msg msg, dhcp_msg reply, int sz)
	{
	if (sz < DHCP_MSG_FIXED_SIZE) {
	if (verbose) LOGD("netcfg: Wrong size %d != %d\n", sz, DHCP_MSG_FIXED_SIZE);
	return 0;
	}
	if (reply->op != OP_BOOTREPLY) {
	if (verbose) LOGD("netcfg: Wrong Op %d != %d\n", reply->op, OP_BOOTREPLY);
	return 0;
	}
	if (reply->xid != msg->xid) {
	if (verbose) LOGD("netcfg: Wrong Xid 0x%x != 0x%x\n", ntohl(reply->xid),
	ntohl(msg->xid));
	return 0;
	}
	if (reply->htype != msg->htype) {
	if (verbose) LOGD("netcfg: Wrong Htype %d != %d\n", reply->htype, msg->htype);
	return 0;
	}
	if (reply->hlen != msg->hlen) {
	if (verbose) LOGD("netcfg: Wrong Hlen %d != %d\n", reply->hlen, msg->hlen);
	return 0;
	}
	if (memcmp(msg->chaddr, reply->chaddr, msg->hlen)) {
	if (verbose) LOGD("netcfg: Wrong chaddr %x != %x\n", (reply->chaddr),(msg->chaddr));
	return 0;
	}
	return 1;
	}

	#define STATE_SELECTING 1
	#define STATE_REQUESTING 2

	#define TIMEOUT_INITIAL 4000
	#define TIMEOUT_MAX 32000

	int dhcp_init_ifc(const char *ifname)
	{
	dhcp_msg discover_msg;
	dhcp_msg request_msg;
	dhcp_msg reply;
	dhcp_msg *msg;
	dhcp_info info;
	int s, r, size;
	int valid_reply;
	uint32_t xid;
	unsigned char hwaddr[6];
	struct pollfd pfd;
	unsigned int state;
	unsigned int timeout;
	int if_index;

	xid = (uint32_t) get_msecs();

	if (ifc_get_hwaddr(ifname, hwaddr)) {
	return fatal("cannot obtain interface address");
	}
	if (ifc_get_ifindex(ifname, &if_index)) {
	return fatal("cannot obtain interface index");
	}

	s = open_raw_socket(ifname, hwaddr, if_index);

	timeout = TIMEOUT_INITIAL;
	state = STATE_SELECTING;
	info.type = 0;
	goto transmit;

	for (;;) {
	pfd.fd = s;
	pfd.events = POLLIN;
	pfd.revents = 0;
	r = poll(&pfd, 1, timeout);

	if (r == 0) {
	#if VERBOSE
	printerr("TIMEOUT\n");
	#endif
	if (timeout >= TIMEOUT_MAX) {
	printerr("timed out\n");
	if ( info.type == DHCPOFFER ) {
	printerr("no acknowledgement from DHCP server\nconfiguring %s with offered parameters\n", ifname);
	return dhcp_configure(ifname, &info);
	}
	errno = ETIME;
	close(s);
	return -1;
	}
	timeout = timeout * 2;

	transmit:
	size = 0;
	msg = NULL;
	switch(state) {
	case STATE_SELECTING:
	msg = &discover_msg;
	size = init_dhcp_discover_msg(msg, hwaddr, xid);
	break;
	case STATE_REQUESTING:
	msg = &request_msg;
	size = init_dhcp_request_msg(msg, hwaddr, xid, info.ipaddr, info.serveraddr);
	break;
	default:
	r = 0;
	}
	if (size != 0) {
	r = send_message(s, if_index, msg, size);
	if (r < 0) {
	printerr("error sending dhcp msg: %s\n", strerror(errno));
	}
	}
	continue;
	}

	if (r < 0) {
	if ((errno == EAGAIN) \|\| (errno == EINTR)) {
	continue;
	}
	return fatal("poll failed");
	}

	errno = 0;
	r = receive_packet(s, &reply);
	if (r < 0) {
	if (errno != 0) {
	LOGD("receive_packet failed (%d): %s", r, strerror(errno));
	if (errno == ENETDOWN \|\| errno == ENXIO) {
	return -1;
	}
	}
	continue;
	}

	#if VERBOSE > 1
	dump_dhcp_msg(&reply, r);
	#endif
	decode_dhcp_msg(&reply, r, &info);

	if (state == STATE_SELECTING) {
	valid_reply = is_valid_reply(&discover_msg, &reply, r);
	} else {
	valid_reply = is_valid_reply(&request_msg, &reply, r);
	}
	if (!valid_reply) {
	printerr("invalid reply\n");
	continue;
	}

	if (verbose) dump_dhcp_info(&info);

	switch(state) {
	case STATE_SELECTING:
	if (info.type == DHCPOFFER) {
	state = STATE_REQUESTING;
	timeout = TIMEOUT_INITIAL;
	xid++;
	goto transmit;
	}
	break;
	case STATE_REQUESTING:
	if (info.type == DHCPACK) {
	printerr("configuring %s\n", ifname);
	close(s);
	return dhcp_configure(ifname, &info);
	} else if (info.type == DHCPNAK) {
	printerr("configuration request denied\n");
	close(s);
	return -1;
	} else {
	printerr("ignoring %s message in state %d\n",
	dhcp_type_to_name(info.type), state);
	}
	break;
	}
	}
	close(s);
	return 0;
	}

	int do_dhcp(char *iname)
	{
	if (ifc_set_addr(iname, 0)) {
	printerr("failed to set ip addr for %s to 0.0.0.0: %s\n", iname, strerror(errno));
	return -1;
	}

	if (ifc_up(iname)) {
	printerr("failed to bring up interface %s: %s\n", iname, strerror(errno));
	return -1;
	}

	return dhcp_init_ifc(iname);
	}