Make arp code more robust and refactor it a bit.
Handle failure to create arp sockets more gracefully. Add initial support for retransmitting arp requests if no reply is met after a certain number of spurious packets.
This commit is contained in:
Nicholas J. Kain
parent
f4aa2058db
commit
a7db2c4bd2
150
ndhc/arp.c
150
ndhc/arp.c
@ -1,5 +1,5 @@
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/* arp.c - arp ping checking
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* Time-stamp: <2011-03-30 23:34:21 nk>
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* Time-stamp: <2011-03-31 02:29:09 nk>
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*
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* Copyright 2010-2011 Nicholas J. Kain <njkain@gmail.com>
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*
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@ -41,38 +41,51 @@
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#include "strl.h"
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#include "io.h"
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#define ARP_MSG_SIZE 0x2a
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#define ARP_RETRY_COUNT 3
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static struct arpMsg arpreply;
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static int arpreply_offset;
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static struct dhcpMessage arp_dhcp_packet;
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static int arp_packet_num;
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/* Returns fd of the arp socket, or -1 on failure. */
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static int arp_close_fd(struct client_state_t *cs)
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{
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if (cs->arpFd != -1) {
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epoll_del(cs, cs->arpFd);
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close(cs->arpFd);
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cs->arpFd = -1;
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return 1;
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}
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return 0;
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}
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/* Returns 0 on success, -1 on failure. */
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static int arpping(struct client_state_t *cs, uint32_t test_ip,
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uint32_t from_ip, uint8_t *from_mac, const char *interface)
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{
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int arpfd;
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int opt = 1;
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struct sockaddr addr; /* for interface name */
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struct arpMsg arp;
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if (cs->arpFd != -1) {
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epoll_del(cs, cs->arpFd);
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close(cs->arpFd);
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}
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arpfd = socket(PF_PACKET, SOCK_PACKET, htons(ETH_P_ARP));
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if (arpfd == -1) {
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log_warning("arpping: failed to create socket: %s", strerror(errno));
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return -1;
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}
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if (cs->arpFd == -1) {
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int arpfd = socket(PF_PACKET, SOCK_PACKET, htons(ETH_P_ARP));
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if (arpfd == -1) {
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log_warning("arpping: failed to create socket: %s", strerror(errno));
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return -1;
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}
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if (setsockopt(arpfd, SOL_SOCKET, SO_BROADCAST,
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&opt, sizeof opt) == -1) {
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log_warning("arpping: failed to set broadcast: %s", strerror(errno));
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close(arpfd);
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return -1;
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if (setsockopt(arpfd, SOL_SOCKET, SO_BROADCAST,
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&opt, sizeof opt) == -1) {
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log_warning("arpping: failed to set broadcast: %s", strerror(errno));
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close(arpfd);
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return -1;
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}
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set_sock_nonblock(arpfd);
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cs->arpFd = arpfd;
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epoll_add(cs, arpfd);
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}
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set_sock_nonblock(arpfd);
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/* send arp request */
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memset(&arp, 0, sizeof arp);
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memset(arp.h_dest, 0xff, 6); /* MAC DA */
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@ -90,60 +103,63 @@ static int arpping(struct client_state_t *cs, uint32_t test_ip,
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memset(&addr, 0, sizeof addr);
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strlcpy(addr.sa_data, interface, sizeof addr.sa_data);
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if (safe_sendto(arpfd, (const char *)&arp, sizeof arp,
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if (safe_sendto(cs->arpFd, (const char *)&arp, sizeof arp,
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0, &addr, sizeof addr) < 0) {
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log_error("arpping: sendto failed: %s", strerror(errno));
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close(arpfd);
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arp_close_fd(cs);
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return -1;
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}
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return arpfd;
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arp_packet_num = 0;
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return 0;
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}
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void arp_check(struct client_state_t *cs, struct dhcpMessage *packet)
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int arp_check(struct client_state_t *cs, struct dhcpMessage *packet)
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{
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if (arpping(cs, arp_dhcp_packet.yiaddr, 0, client_config.arp,
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client_config.interface) == -1)
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return -1;
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cs->arpPrevState = cs->dhcpState;
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cs->dhcpState = DS_ARP_CHECK;
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memcpy(&arp_dhcp_packet, packet, sizeof (struct dhcpMessage));
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cs->arpFd = arpping(cs, arp_dhcp_packet.yiaddr, 0, client_config.arp,
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client_config.interface);
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epoll_add(cs, cs->arpFd);
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cs->timeout = 2000;
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memcpy(&arp_dhcp_packet, packet, sizeof (struct dhcpMessage));
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memset(&arpreply, 0, sizeof arpreply);
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arpreply_offset = 0;
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return 0;
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}
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void arp_gw_check(struct client_state_t *cs)
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int arp_gw_check(struct client_state_t *cs)
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{
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if (arpping(cs, cs->routerAddr, 0, client_config.arp,
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client_config.interface) == -1)
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return -1;
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cs->arpPrevState = cs->dhcpState;
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cs->dhcpState = DS_ARP_GW_CHECK;
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memset(&arp_dhcp_packet, 0, sizeof (struct dhcpMessage));
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cs->arpFd = arpping(cs, cs->routerAddr, 0, client_config.arp,
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client_config.interface);
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epoll_add(cs, cs->arpFd);
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cs->oldTimeout = cs->timeout;
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cs->timeout = 2000;
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memset(&arp_dhcp_packet, 0, sizeof (struct dhcpMessage));
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memset(&arpreply, 0, sizeof arpreply);
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arpreply_offset = 0;
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return 0;
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}
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void arp_get_gw_hwaddr(struct client_state_t *cs)
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int arp_get_gw_hwaddr(struct client_state_t *cs)
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{
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if (cs->dhcpState != DS_BOUND)
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log_warning("arp_get_gw_hwaddr: called when state != DS_BOUND");
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if (arpping(cs, cs->routerAddr, 0, client_config.arp,
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client_config.interface) == -1)
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return -1;
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log_line("arp_get_hw_addr: searching for gw address");
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memset(&arp_dhcp_packet, 0, sizeof (struct dhcpMessage));
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cs->arpFd = arpping(cs, cs->routerAddr, 0, client_config.arp,
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client_config.interface);
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epoll_add(cs, cs->arpFd);
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memset(&arpreply, 0, sizeof arpreply);
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arpreply_offset = 0;
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return 0;
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}
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static void arp_failed(struct client_state_t *cs)
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{
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log_line("Offered address is in use: declining.");
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epoll_del(cs, cs->arpFd);
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close(cs->arpFd);
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cs->arpFd = -1;
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arp_close_fd(cs);
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send_decline(cs->xid, cs->serverAddr, arp_dhcp_packet.yiaddr);
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if (cs->arpPrevState != DS_REQUESTING)
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@ -158,9 +174,7 @@ static void arp_failed(struct client_state_t *cs)
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void arp_gw_failed(struct client_state_t *cs)
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{
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log_line("arp: gateway appears to have changed, getting new lease");
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epoll_del(cs, cs->arpFd);
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close(cs->arpFd);
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cs->arpFd = -1;
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arp_close_fd(cs);
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// Same as packet.c: line 258
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ifchange(NULL, IFCHANGE_DECONFIG);
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@ -176,9 +190,7 @@ void arp_success(struct client_state_t *cs)
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{
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struct in_addr temp_addr;
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epoll_del(cs, cs->arpFd);
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close(cs->arpFd);
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cs->arpFd = -1;
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arp_close_fd(cs);
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/* enter bound state */
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cs->t1 = cs->lease >> 1;
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@ -206,9 +218,8 @@ void arp_success(struct client_state_t *cs)
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void arp_gw_success(struct client_state_t *cs)
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{
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log_line("arp: gateway seems unchanged");
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epoll_del(cs, cs->arpFd);
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close(cs->arpFd);
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cs->arpFd = -1;
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arp_close_fd(cs);
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cs->timeout = cs->oldTimeout;
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cs->dhcpState = cs->arpPrevState;
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}
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@ -220,12 +231,13 @@ void handle_arp_response(struct client_state_t *cs)
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int r = safe_read(cs->arpFd, (char *)&arpreply + arpreply_offset,
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sizeof arpreply - arpreply_offset);
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if (r < 0) {
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// Conservative responses: assume failure.
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if (cs->dhcpState == DS_ARP_CHECK)
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arp_failed(cs);
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else
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arp_gw_failed(cs);
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return;
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log_warning("handle_arp_response: short read");
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switch (cs->dhcpState) {
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case DS_ARP_CHECK: arp_failed(cs); break;
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case DS_ARP_GW_CHECK: arp_gw_failed(cs); break;
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case DS_BOUND: break; // keep trying for finding gw mac
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default: break;
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}
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} else
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arpreply_offset += r;
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}
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@ -234,6 +246,8 @@ void handle_arp_response(struct client_state_t *cs)
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log_warning("handle_arp_response: Received short ARP message.");
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return;
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}
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++arp_packet_num;
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switch (cs->dhcpState) {
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case DS_ARP_CHECK:
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if (arpreply.operation == htons(ARPOP_REPLY)
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@ -246,7 +260,9 @@ void handle_arp_response(struct client_state_t *cs)
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arp_success(cs);
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else
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arp_failed(cs);
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return;
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} else {
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log_line("arp ping noise while waiting for check timeout");
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memset(&arpreply, 0, sizeof arpreply);
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arpreply_offset = 0;
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}
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@ -261,7 +277,9 @@ void handle_arp_response(struct client_state_t *cs)
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arp_gw_success(cs);
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else
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arp_gw_failed(cs);
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return;
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} else {
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log_line("still waiting for gateway to reply to arp ping");
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memset(&arpreply, 0, sizeof arpreply);
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arpreply_offset = 0;
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}
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@ -272,13 +290,13 @@ void handle_arp_response(struct client_state_t *cs)
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&& *(aliased_uint32_t*)arpreply.sInaddr == cs->routerAddr)
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{
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memcpy(cs->routerArp, arpreply.sHaddr, 6);
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epoll_del(cs, cs->arpFd);
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close(cs->arpFd);
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cs->arpFd = -1;
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arp_close_fd(cs);
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log_line("gateway hardware address %02x:%02x:%02x:%02x:%02x:%02x",
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cs->routerArp[0], cs->routerArp[1],
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cs->routerArp[2], cs->routerArp[3],
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cs->routerArp[4], cs->routerArp[5]);
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return;
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} else {
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log_line("still looking for gateway hardware address");
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memset(&arpreply, 0, sizeof arpreply);
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@ -286,11 +304,21 @@ void handle_arp_response(struct client_state_t *cs)
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}
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break;
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default:
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epoll_del(cs, cs->arpFd);
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close(cs->arpFd);
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cs->arpFd = -1;
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arp_close_fd(cs);
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log_warning("handle_arp_response: called in invalid state 0x%02x",
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cs->dhcpState);
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break;
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return;
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}
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if (arp_packet_num >= ARP_RETRY_COUNT) {
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switch (cs->dhcpState) {
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case DS_BOUND:
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if (arpping(cs, cs->routerAddr, 0, client_config.arp,
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client_config.interface) == -1)
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log_line("failed to retransmit arp packet for finding gw mac addr");
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break;
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default:
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log_line("not yet bothering with arp retransmit for non-DS_BOUND state");
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break;
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}
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}
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}
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14
ndhc/arp.h
14
ndhc/arp.h
@ -1,5 +1,5 @@
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/* arp.h - functions to call the interface change daemon
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* Time-stamp: <2011-03-30 23:36:45 nk>
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* Time-stamp: <2011-03-31 02:28:59 nk>
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*
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* Copyright 2010-2011 Nicholas J. Kain <njkain@gmail.com>
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*
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@ -49,15 +49,11 @@ struct arpMsg {
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uint8_t pad[18]; /* 2a pad for min. ethernet payload (60 bytes) */
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};
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enum {
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ARP_MSG_SIZE = 0x2a
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};
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void arp_check(struct client_state_t *cs, struct dhcpMessage *packet);
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int arp_check(struct client_state_t *cs, struct dhcpMessage *packet);
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int arp_gw_check(struct client_state_t *cs);
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int arp_get_gw_hwaddr(struct client_state_t *cs);
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void arp_success(struct client_state_t *cs);
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void handle_arp_response(struct client_state_t *cs);
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void arp_gw_check(struct client_state_t *cs);
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void arp_gw_failed(struct client_state_t *cs);
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void arp_get_gw_hwaddr(struct client_state_t *cs);
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void handle_arp_response(struct client_state_t *cs);
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#endif /* ARPPING_H_ */
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@ -1,5 +1,5 @@
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/* config.h - internal configuration and state for ndhc
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* Time-stamp: <2011-03-30 23:33:07 nk>
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* Time-stamp: <2011-03-31 01:38:03 nk>
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*
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* (c) 2004-2011 Nicholas J. Kain <njkain at gmail dot com>
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*
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@ -1,5 +1,5 @@
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/* ifchange.c - functions to call the interface change daemon
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* Time-stamp: <2011-03-30 22:54:28 nk>
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* Time-stamp: <2011-03-31 01:57:46 nk>
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*
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* (c) 2004-2011 Nicholas J. Kain <njkain at gmail dot com>
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*
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@ -226,8 +226,12 @@ static void bound_if(struct dhcpMessage *packet)
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send_cmd(sockfd, packet, DHCP_WINS_SERVER);
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close(sockfd);
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if (router_set == 1)
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arp_get_gw_hwaddr(&cs);
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if (router_set == 1) {
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if (arp_get_gw_hwaddr(&cs) == -1) {
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log_warning("arp_get_gw_hwaddr failed to make arp socket; setting gw mac=ff:ff:ff:ff:ff:ff");
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memset(&cs.routerAddr, 0xff, 4);
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}
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}
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}
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void ifchange(struct dhcpMessage *packet, int mode)
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@ -1,5 +1,5 @@
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/* ndhc.c - DHCP client
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* Time-stamp: <2011-03-30 23:58:05 nk>
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* Time-stamp: <2011-03-31 01:38:17 nk>
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*
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* (c) 2004-2011 Nicholas J. Kain <njkain at gmail dot com>
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*
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@ -155,7 +155,8 @@ static void nl_handlemsg(struct nlmsghdr *msg, unsigned int len,
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* If we don't have a lease, state -> INIT.
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*/
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if (cs->dhcpState == DS_BOUND) {
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arp_gw_check(cs);
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if (arp_gw_check(cs) == -1)
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log_warning("arp_gw_check could not make arp socket, assuming lease is still OK");
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} else if (cs->dhcpState != DS_INIT_SELECTING)
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takedown_if(cs);
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}
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@ -1,5 +1,5 @@
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/* packet.c - send and react to DHCP message packets
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* Time-stamp: <2011-03-31 00:01:50 nk>
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* Time-stamp: <2011-03-31 01:59:17 nk>
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*
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* (c) 2004-2011 Nicholas J. Kain <njkain at gmail dot com>
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* (c) 2001 Russ Dill <Russ.Dill@asu.edu>
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@ -279,8 +279,16 @@ static void dhcp_ack_or_nak_packet(struct client_state_t *cs,
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cs->lease = RETRY_DELAY;
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}
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arp_check(cs, packet);
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// Can transition from DS_ARP_CHECK to DS_BOUND or DS_INIT_SELECTING.
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if (arp_check(cs, packet) == -1) {
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log_warning("arp_check failed to make arp socket, retrying lease");
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ifchange(NULL, IFCHANGE_DECONFIG);
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cs->dhcpState = DS_INIT_SELECTING;
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cs->timeout = 30000;
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cs->requestedIP = 0;
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cs->packetNum = 0;
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change_listen_mode(cs, LM_RAW);
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}
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} else if (*message == DHCPNAK) {
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/* return to init state */
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