* certainly be used. Its naming is built over multicast DNS.
*/
-// #define DEBUG
+//#define DEBUG
// TODO:
// - more real-world usage/testing, especially daemon mode
struct arp_packet {
struct ether_header hdr;
- // FIXME this part is netinet/if_ether.h "struct ether_arp"
- struct arphdr arp;
- struct ether_addr source_addr;
- struct in_addr source_ip;
- struct ether_addr target_addr;
- struct in_addr target_ip;
+ struct ether_arp arp;
} ATTRIBUTE_PACKED;
enum {
DEFEND_INTERVAL = 10
};
-static const struct in_addr null_ip = { 0 };
-static const struct ether_addr null_addr = { {0, 0, 0, 0, 0, 0} };
+/* States during the configuration process. */
+enum {
+ PROBE = 0,
+ RATE_LIMIT_PROBE,
+ ANNOUNCE,
+ MONITOR,
+ DEFEND
+};
-static int verbose = 0;
+/* Implicitly zero-initialized */
+static const struct in_addr null_ip;
+static const struct ether_addr null_addr;
+static int verbose;
#define DBG(fmt,args...) \
do { } while (0)
const struct ether_addr *target_addr, struct in_addr target_ip)
{
struct arp_packet p;
+ memset(&p, 0, sizeof(p));
// ether header
p.hdr.ether_type = htons(ETHERTYPE_ARP);
memset(p.hdr.ether_dhost, 0xff, ETH_ALEN);
// arp request
- p.arp.ar_hrd = htons(ARPHRD_ETHER);
- p.arp.ar_pro = htons(ETHERTYPE_IP);
- p.arp.ar_hln = ETH_ALEN;
- p.arp.ar_pln = 4;
- p.arp.ar_op = htons(op);
- memcpy(&p.source_addr, source_addr, ETH_ALEN);
- memcpy(&p.source_ip, &source_ip, sizeof (p.source_ip));
- memcpy(&p.target_addr, target_addr, ETH_ALEN);
- memcpy(&p.target_ip, &target_ip, sizeof (p.target_ip));
+ p.arp.arp_hrd = htons(ARPHRD_ETHER);
+ p.arp.arp_pro = htons(ETHERTYPE_IP);
+ p.arp.arp_hln = ETH_ALEN;
+ p.arp.arp_pln = 4;
+ p.arp.arp_op = htons(op);
+ memcpy(&p.arp.arp_sha, source_addr, ETH_ALEN);
+ memcpy(&p.arp.arp_spa, &source_ip, sizeof (p.arp.arp_spa));
+ memcpy(&p.arp.arp_tha, target_addr, ETH_ALEN);
+ memcpy(&p.arp.arp_tpa, &target_ip, sizeof (p.arp.arp_tpa));
// send it
if (sendto(fd, &p, sizeof (p), 0, saddr, sizeof (*saddr)) < 0) {
int fd;
int ready = 0;
suseconds_t timeout = 0; // milliseconds
- time_t defend = 0;
unsigned conflicts = 0;
unsigned nprobes = 0;
unsigned nclaims = 0;
int t;
+ int state = PROBE;
// parse commandline: prog [options] ifname script
while ((t = getopt(argc, argv, "fqr:v")) != EOF) {
fds[0].events = POLLIN;
fds[0].revents = 0;
+ int source_ip_conflict = 0;
+ int target_ip_conflict = 0;
+
// poll, being ready to adjust current timeout
if (!timeout) {
timeout = ms_rdelay(PROBE_WAIT);
// make the kernel filter out all packets except
// ones we'd care about.
}
+ // set tv1 to the point in time when we timeout
gettimeofday(&tv1, NULL);
tv1.tv_usec += (timeout % 1000) * 1000;
while (tv1.tv_usec > 1000000) {
timeout, intf, nprobes, nclaims);
switch (poll(fds, 1, timeout)) {
- // timeouts trigger protocol transitions
+ // timeout
case 0:
- // probes
- if (nprobes < PROBE_NUM) {
- nprobes++;
- VDBG("probe/%d %s@%s\n",
- nprobes, intf, inet_ntoa(ip));
- (void)arp(fd, &saddr, ARPOP_REQUEST,
- &addr, null_ip,
- &null_addr, ip);
+ VDBG("state = %d\n", state);
+ switch (state) {
+ case PROBE:
+ // timeouts in the PROBE state means no conflicting ARP packets
+ // have been received, so we can progress through the states
if (nprobes < PROBE_NUM) {
+ nprobes++;
+ VDBG("probe/%d %s@%s\n",
+ nprobes, intf, inet_ntoa(ip));
+ (void)arp(fd, &saddr, ARPOP_REQUEST,
+ &addr, null_ip,
+ &null_addr, ip);
timeout = PROBE_MIN * 1000;
timeout += ms_rdelay(PROBE_MAX
- PROBE_MIN);
- } else
- timeout = ANNOUNCE_WAIT * 1000;
- }
- // then announcements
- else if (nclaims < ANNOUNCE_NUM) {
- nclaims++;
+ }
+ else {
+ // Switch to announce state.
+ state = ANNOUNCE;
+ nclaims = 0;
+ VDBG("announce/%d %s@%s\n",
+ nclaims, intf, inet_ntoa(ip));
+ (void)arp(fd, &saddr, ARPOP_REQUEST,
+ &addr, ip,
+ &addr, ip);
+ timeout = ANNOUNCE_INTERVAL * 1000;
+ }
+ break;
+ case RATE_LIMIT_PROBE:
+ // timeouts in the RATE_LIMIT_PROBE state means no conflicting ARP packets
+ // have been received, so we can move immediately to the announce state
+ state = ANNOUNCE;
+ nclaims = 0;
VDBG("announce/%d %s@%s\n",
nclaims, intf, inet_ntoa(ip));
(void)arp(fd, &saddr, ARPOP_REQUEST,
&addr, ip,
&addr, ip);
+ timeout = ANNOUNCE_INTERVAL * 1000;
+ break;
+ case ANNOUNCE:
+ // timeouts in the ANNOUNCE state means no conflicting ARP packets
+ // have been received, so we can progress through the states
if (nclaims < ANNOUNCE_NUM) {
+ nclaims++;
+ VDBG("announce/%d %s@%s\n",
+ nclaims, intf, inet_ntoa(ip));
+ (void)arp(fd, &saddr, ARPOP_REQUEST,
+ &addr, ip,
+ &addr, ip);
timeout = ANNOUNCE_INTERVAL * 1000;
- } else {
+ }
+ else {
+ // Switch to monitor state.
+ state = MONITOR;
// link is ok to use earlier
+ // FIXME update filters
run(script, "config", intf, &ip);
ready = 1;
conflicts = 0;
- timeout = -1;
+ timeout = -1; // Never timeout in the monitor state.
// NOTE: all other exit paths
// should deconfig ...
if (quit)
return EXIT_SUCCESS;
- // FIXME update filters
}
- }
- break;
-
+ break;
+ case DEFEND:
+ // We won! No ARP replies, so just go back to monitor.
+ state = MONITOR;
+ timeout = -1;
+ conflicts = 0;
+ break;
+ default:
+ // Invalid, should never happen. Restart the whole protocol.
+ state = PROBE;
+ pick(&ip);
+ timeout = 0;
+ nprobes = 0;
+ nclaims = 0;
+ break;
+ } // switch (state)
+ break; // case 0 (timeout)
// packets arriving
case 1:
- // maybe adjust timeout
+ // We need to adjust the timeout in case we didn't receive
+ // a conflicting packet.
if (timeout > 0) {
struct timeval tv2;
gettimeofday(&tv2, NULL);
if (timercmp(&tv1, &tv2, <)) {
+ // Current time is greater than the expected timeout time.
+ // Should never happen.
+ VDBG("missed an expected timeout\n");
timeout = 0;
} else {
+ VDBG("adjusting timeout\n");
timersub(&tv1, &tv2, &tv1);
timeout = 1000 * tv1.tv_sec
+ tv1.tv_usec / 1000;
}
}
+
if ((fds[0].revents & POLLIN) == 0) {
if (fds[0].revents & POLLERR) {
// FIXME: links routinely go down;
}
continue;
}
+
// read ARP packet
if (recv(fd, &p, sizeof (p), 0) < 0) {
why = "recv";
if (p.hdr.ether_type != htons(ETHERTYPE_ARP))
continue;
- VDBG("%s recv arp type=%d, op=%d,\n",
+#ifdef DEBUG
+ {
+ struct ether_addr * sha = (struct ether_addr *) p.arp.arp_sha;
+ struct ether_addr * tha = (struct ether_addr *) p.arp.arp_tha;
+ struct in_addr * spa = (struct in_addr *) p.arp.arp_spa;
+ struct in_addr * tpa = (struct in_addr *) p.arp.arp_tpa;
+ VDBG("%s recv arp type=%d, op=%d,\n",
intf, ntohs(p.hdr.ether_type),
- ntohs(p.arp.ar_op));
- VDBG("\tsource=%s %s\n",
- ether_ntoa(&p.source_addr),
- inet_ntoa(p.source_ip));
- VDBG("\ttarget=%s %s\n",
- ether_ntoa(&p.target_addr),
- inet_ntoa(p.target_ip));
- if (p.arp.ar_op != htons(ARPOP_REQUEST)
- && p.arp.ar_op != htons(ARPOP_REPLY))
+ ntohs(p.arp.arp_op));
+ VDBG("\tsource=%s %s\n",
+ ether_ntoa(sha),
+ inet_ntoa(*spa));
+ VDBG("\ttarget=%s %s\n",
+ ether_ntoa(tha),
+ inet_ntoa(*tpa));
+ }
+#endif
+ if (p.arp.arp_op != htons(ARPOP_REQUEST)
+ && p.arp.arp_op != htons(ARPOP_REPLY))
continue;
- // some cases are always conflicts
- if ((p.source_ip.s_addr == ip.s_addr)
- && (memcmp(&addr, &p.source_addr,
- ETH_ALEN) != 0)) {
-collision:
- VDBG("%s ARP conflict from %s\n", intf,
- ether_ntoa(&p.source_addr));
- if (ready) {
- time_t now = time(0);
-
- if ((defend + DEFEND_INTERVAL)
- < now) {
- defend = now;
- (void)arp(fd, &saddr,
- ARPOP_REQUEST,
- &addr, ip,
- &addr, ip);
- VDBG("%s defend\n", intf);
- timeout = -1;
- continue;
+ if (memcmp(p.arp.arp_spa, &ip.s_addr, sizeof(struct in_addr)) == 0 &&
+ memcmp(&addr, &p.arp.arp_sha, ETH_ALEN) != 0) {
+ source_ip_conflict = 1;
+ }
+ if (memcmp(p.arp.arp_tpa, &ip.s_addr, sizeof(struct in_addr)) == 0 &&
+ p.arp.arp_op == htons(ARPOP_REQUEST) &&
+ memcmp(&addr, &p.arp.arp_tha, ETH_ALEN) != 0) {
+ target_ip_conflict = 1;
+ }
+
+ VDBG("state = %d, source ip conflict = %d, target ip conflict = %d\n",
+ state, source_ip_conflict, target_ip_conflict);
+ switch (state) {
+ case PROBE:
+ case ANNOUNCE:
+ // When probing or announcing, check for source IP conflicts
+ // and other hosts doing ARP probes (target IP conflicts).
+ if (source_ip_conflict || target_ip_conflict) {
+ conflicts++;
+ if (conflicts >= MAX_CONFLICTS) {
+ VDBG("%s ratelimit\n", intf);
+ timeout = RATE_LIMIT_INTERVAL * 1000;
+ state = RATE_LIMIT_PROBE;
}
- defend = now;
+
+ // restart the whole protocol
+ pick(&ip);
+ timeout = 0;
+ nprobes = 0;
+ nclaims = 0;
+ }
+ break;
+ case MONITOR:
+ // If a conflict, we try to defend with a single ARP probe.
+ if (source_ip_conflict) {
+ VDBG("monitor conflict -- defending\n");
+ state = DEFEND;
+ timeout = DEFEND_INTERVAL * 1000;
+ (void)arp(fd, &saddr,
+ ARPOP_REQUEST,
+ &addr, ip,
+ &addr, ip);
+ }
+ break;
+ case DEFEND:
+ // Well, we tried. Start over (on conflict).
+ if (source_ip_conflict) {
+ state = PROBE;
+ VDBG("defend conflict -- starting over\n");
ready = 0;
run(script, "deconfig", intf, &ip);
- // FIXME rm filters: setsockopt(fd,
- // SO_DETACH_FILTER, ...)
- }
- conflicts++;
- if (conflicts >= MAX_CONFLICTS) {
- VDBG("%s ratelimit\n", intf);
- sleep(RATE_LIMIT_INTERVAL);
+
+ // restart the whole protocol
+ pick(&ip);
+ timeout = 0;
+ nprobes = 0;
+ nclaims = 0;
}
- // restart the whole protocol
+ break;
+ default:
+ // Invalid, should never happen. Restart the whole protocol.
+ VDBG("invalid state -- starting over\n");
+ state = PROBE;
pick(&ip);
timeout = 0;
nprobes = 0;
nclaims = 0;
- }
- // two hosts probing one address is a collision too
- else if (p.target_ip.s_addr == ip.s_addr
- && nclaims == 0
- && p.arp.ar_op == htons(ARPOP_REQUEST)
- && memcmp(&addr, &p.target_addr,
- ETH_ALEN) != 0) {
- goto collision;
- }
- break;
+ break;
+ } // switch state
+ break; // case 1 (packets arriving)
default:
why = "poll";
goto bad;
- }
+ } // switch poll
}
bad:
if (foreground)
projects / oweals / busybox.git / commitdiff