With new code, we request that target IP (server ID) must be directly reachable. If it's not, this happens: udhcpc: waiting 2000 seconds udhcpc: entering listen mode: kernel udhcpc: opening listen socket on *:68 wlan0 udhcpc: entering renew state udhcpc: sending renew to 1.1.1.1 udhcpc: send: Network is unreachable ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 1.1.1.1 needs routing, this is fishy! udhcpc: entering rebinding state udhcpc: entering listen mode: raw udhcpc: created raw socket udhcpc: sending renew to 0.0.0.0 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ going to use broadcast which is the desired behavior. Before the patch, packet to 1.1.1.1 was routed over eth0 (!) and maybe even into Internet (!!!). function old new delta udhcpc_main 2752 2763 +11 udhcp_send_kernel_packet 295 301 +6 send_renew 82 84 +2 send_packet 166 168 +2 bcast_or_ucast 23 25 +2 ------------------------------------------------------------------------------ (add/remove: 0/0 grow/shrink: 5/0 up/down: 23/0) Total: 23 bytes Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
242 lines
6.3 KiB
C
242 lines
6.3 KiB
C
/* vi: set sw=4 ts=4: */
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/*
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* Packet ops
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*
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* Rewrite by Russ Dill <Russ.Dill@asu.edu> July 2001
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*
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* Licensed under GPLv2, see file LICENSE in this source tree.
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*/
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#include "common.h"
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#include "dhcpd.h"
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#include <netinet/in.h>
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#include <netinet/if_ether.h>
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#include <netpacket/packet.h>
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#if ENABLE_UDHCPC || ENABLE_UDHCPD
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void FAST_FUNC udhcp_init_header(struct dhcp_packet *packet, char type)
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{
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memset(packet, 0, sizeof(*packet));
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packet->op = BOOTREQUEST; /* if client to a server */
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switch (type) {
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case DHCPOFFER:
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case DHCPACK:
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case DHCPNAK:
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packet->op = BOOTREPLY; /* if server to client */
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}
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packet->htype = 1; /* ethernet */
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packet->hlen = 6;
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packet->cookie = htonl(DHCP_MAGIC);
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if (DHCP_END != 0)
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packet->options[0] = DHCP_END;
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udhcp_add_simple_option(packet, DHCP_MESSAGE_TYPE, type);
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}
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#endif
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#if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 2
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void FAST_FUNC udhcp_dump_packet(struct dhcp_packet *packet)
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{
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char buf[sizeof(packet->chaddr)*2 + 1];
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if (dhcp_verbose < 2)
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return;
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bb_error_msg(
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//"op %x"
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//" htype %x"
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" hlen %x"
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//" hops %x"
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" xid %x"
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//" secs %x"
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//" flags %x"
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" ciaddr %x"
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" yiaddr %x"
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" siaddr %x"
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" giaddr %x"
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//" chaddr %s"
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//" sname %s"
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//" file %s"
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//" cookie %x"
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//" options %s"
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//, packet->op
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//, packet->htype
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, packet->hlen
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//, packet->hops
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, packet->xid
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//, packet->secs
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//, packet->flags
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, packet->ciaddr
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, packet->yiaddr
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, packet->siaddr_nip
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, packet->gateway_nip
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//, packet->chaddr[16]
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//, packet->sname[64]
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//, packet->file[128]
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//, packet->cookie
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//, packet->options[]
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);
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*bin2hex(buf, (void *) packet->chaddr, sizeof(packet->chaddr)) = '\0';
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bb_error_msg("chaddr %s", buf);
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}
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#endif
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/* Read a packet from socket fd, return -1 on read error, -2 on packet error */
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int FAST_FUNC udhcp_recv_kernel_packet(struct dhcp_packet *packet, int fd)
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{
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int bytes;
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memset(packet, 0, sizeof(*packet));
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bytes = safe_read(fd, packet, sizeof(*packet));
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if (bytes < 0) {
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log1("packet read error, ignoring");
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return bytes; /* returns -1 */
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}
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if (bytes < offsetof(struct dhcp_packet, options)
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|| packet->cookie != htonl(DHCP_MAGIC)
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) {
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bb_error_msg("packet with bad magic, ignoring");
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return -2;
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}
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log1("received %s", "a packet");
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udhcp_dump_packet(packet);
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return bytes;
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}
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/* Construct a ip/udp header for a packet, send packet */
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int FAST_FUNC udhcp_send_raw_packet(struct dhcp_packet *dhcp_pkt,
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uint32_t source_nip, int source_port,
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uint32_t dest_nip, int dest_port, const uint8_t *dest_arp,
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int ifindex)
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{
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struct sockaddr_ll dest_sll;
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struct ip_udp_dhcp_packet packet;
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unsigned padding;
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int fd;
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int result = -1;
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const char *msg;
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fd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP));
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if (fd < 0) {
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msg = "socket(%s)";
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goto ret_msg;
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}
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memset(&dest_sll, 0, sizeof(dest_sll));
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memset(&packet, 0, offsetof(struct ip_udp_dhcp_packet, data));
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packet.data = *dhcp_pkt; /* struct copy */
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dest_sll.sll_family = AF_PACKET;
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dest_sll.sll_protocol = htons(ETH_P_IP);
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dest_sll.sll_ifindex = ifindex;
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/*dest_sll.sll_hatype = ARPHRD_???;*/
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/*dest_sll.sll_pkttype = PACKET_???;*/
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dest_sll.sll_halen = 6;
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memcpy(dest_sll.sll_addr, dest_arp, 6);
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if (bind(fd, (struct sockaddr *)&dest_sll, sizeof(dest_sll)) < 0) {
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msg = "bind(%s)";
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goto ret_close;
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}
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/* We were sending full-sized DHCP packets (zero padded),
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* but some badly configured servers were seen dropping them.
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* Apparently they drop all DHCP packets >576 *ethernet* octets big,
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* whereas they may only drop packets >576 *IP* octets big
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* (which for typical Ethernet II means 590 octets: 6+6+2 + 576).
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*
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* In order to work with those buggy servers,
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* we truncate packets after end option byte.
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*
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* However, RFC 1542 says "The IP Total Length and UDP Length
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* must be large enough to contain the minimal BOOTP header of 300 octets".
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* Thus, we retain enough padding to not go below 300 BOOTP bytes.
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* Some devices have filters which drop DHCP packets shorter than that.
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*/
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padding = DHCP_OPTIONS_BUFSIZE - 1 - udhcp_end_option(packet.data.options);
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if (padding > DHCP_SIZE - 300)
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padding = DHCP_SIZE - 300;
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packet.ip.protocol = IPPROTO_UDP;
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packet.ip.saddr = source_nip;
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packet.ip.daddr = dest_nip;
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packet.udp.source = htons(source_port);
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packet.udp.dest = htons(dest_port);
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/* size, excluding IP header: */
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packet.udp.len = htons(UDP_DHCP_SIZE - padding);
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/* for UDP checksumming, ip.len is set to UDP packet len */
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packet.ip.tot_len = packet.udp.len;
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packet.udp.check = inet_cksum((uint16_t *)&packet,
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IP_UDP_DHCP_SIZE - padding);
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/* but for sending, it is set to IP packet len */
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packet.ip.tot_len = htons(IP_UDP_DHCP_SIZE - padding);
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packet.ip.ihl = sizeof(packet.ip) >> 2;
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packet.ip.version = IPVERSION;
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packet.ip.ttl = IPDEFTTL;
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packet.ip.check = inet_cksum((uint16_t *)&packet.ip, sizeof(packet.ip));
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udhcp_dump_packet(dhcp_pkt);
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result = sendto(fd, &packet, IP_UDP_DHCP_SIZE - padding, /*flags:*/ 0,
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(struct sockaddr *) &dest_sll, sizeof(dest_sll));
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msg = "sendto";
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ret_close:
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close(fd);
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if (result < 0) {
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ret_msg:
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bb_perror_msg(msg, "PACKET");
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}
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return result;
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}
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/* Let the kernel do all the work for packet generation */
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int FAST_FUNC udhcp_send_kernel_packet(struct dhcp_packet *dhcp_pkt,
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uint32_t source_nip, int source_port,
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uint32_t dest_nip, int dest_port,
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int send_flags)
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{
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struct sockaddr_in sa;
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unsigned padding;
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int fd;
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int result = -1;
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const char *msg;
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fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP);
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if (fd < 0) {
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msg = "socket(%s)";
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goto ret_msg;
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}
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setsockopt_reuseaddr(fd);
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memset(&sa, 0, sizeof(sa));
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sa.sin_family = AF_INET;
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sa.sin_port = htons(source_port);
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sa.sin_addr.s_addr = source_nip;
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if (bind(fd, (struct sockaddr *)&sa, sizeof(sa)) == -1) {
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msg = "bind(%s)";
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goto ret_close;
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}
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memset(&sa, 0, sizeof(sa));
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sa.sin_family = AF_INET;
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sa.sin_port = htons(dest_port);
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sa.sin_addr.s_addr = dest_nip;
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if (connect(fd, (struct sockaddr *)&sa, sizeof(sa)) == -1) {
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msg = "connect";
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goto ret_close;
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}
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udhcp_dump_packet(dhcp_pkt);
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padding = DHCP_OPTIONS_BUFSIZE - 1 - udhcp_end_option(dhcp_pkt->options);
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if (padding > DHCP_SIZE - 300)
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padding = DHCP_SIZE - 300;
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result = send(fd, dhcp_pkt, DHCP_SIZE - padding, send_flags);
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msg = "send";
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ret_close:
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close(fd);
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if (result < 0) {
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ret_msg:
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bb_perror_msg(msg, "UDP");
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}
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return result;
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}
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