zcip: apply patch from
http://bugs.busybox.net/view.php?id=1005 zcip does not claim another IP after defending
This commit is contained in:
Denis Vlasenko
parent
06ab5fb6b9
commit
87d80dcc3e
@ -15,7 +15,7 @@
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* certainly be used. Its naming is built over multicast DNS.
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*/
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// #define DEBUG
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//#define DEBUG
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// TODO:
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// - more real-world usage/testing, especially daemon mode
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@ -43,12 +43,7 @@
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struct arp_packet {
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struct ether_header hdr;
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// FIXME this part is netinet/if_ether.h "struct ether_arp"
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struct arphdr arp;
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struct ether_addr source_addr;
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struct in_addr source_ip;
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struct ether_addr target_addr;
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struct in_addr target_ip;
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struct ether_arp arp;
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} ATTRIBUTE_PACKED;
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enum {
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@ -68,10 +63,19 @@ enum {
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DEFEND_INTERVAL = 10
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};
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static const struct in_addr null_ip = { 0 };
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static const struct ether_addr null_addr = { {0, 0, 0, 0, 0, 0} };
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/* States during the configuration process. */
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enum {
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PROBE = 0,
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RATE_LIMIT_PROBE,
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ANNOUNCE,
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MONITOR,
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DEFEND
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};
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static int verbose = 0;
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/* Implicitly zero-initialized */
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static const struct in_addr null_ip;
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static const struct ether_addr null_addr;
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static int verbose;
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#define DBG(fmt,args...) \
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do { } while (0)
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@ -100,6 +104,7 @@ static int arp(int fd, struct sockaddr *saddr, int op,
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const struct ether_addr *target_addr, struct in_addr target_ip)
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{
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struct arp_packet p;
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memset(&p, 0, sizeof(p));
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// ether header
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p.hdr.ether_type = htons(ETHERTYPE_ARP);
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@ -107,15 +112,15 @@ static int arp(int fd, struct sockaddr *saddr, int op,
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memset(p.hdr.ether_dhost, 0xff, ETH_ALEN);
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// arp request
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p.arp.ar_hrd = htons(ARPHRD_ETHER);
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p.arp.ar_pro = htons(ETHERTYPE_IP);
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p.arp.ar_hln = ETH_ALEN;
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p.arp.ar_pln = 4;
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p.arp.ar_op = htons(op);
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memcpy(&p.source_addr, source_addr, ETH_ALEN);
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memcpy(&p.source_ip, &source_ip, sizeof (p.source_ip));
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memcpy(&p.target_addr, target_addr, ETH_ALEN);
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memcpy(&p.target_ip, &target_ip, sizeof (p.target_ip));
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p.arp.arp_hrd = htons(ARPHRD_ETHER);
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p.arp.arp_pro = htons(ETHERTYPE_IP);
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p.arp.arp_hln = ETH_ALEN;
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p.arp.arp_pln = 4;
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p.arp.arp_op = htons(op);
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memcpy(&p.arp.arp_sha, source_addr, ETH_ALEN);
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memcpy(&p.arp.arp_spa, &source_ip, sizeof (p.arp.arp_spa));
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memcpy(&p.arp.arp_tha, target_addr, ETH_ALEN);
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memcpy(&p.arp.arp_tpa, &target_ip, sizeof (p.arp.arp_tpa));
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// send it
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if (sendto(fd, &p, sizeof (p), 0, saddr, sizeof (*saddr)) < 0) {
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@ -196,11 +201,11 @@ int zcip_main(int argc, char *argv[])
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int fd;
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int ready = 0;
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suseconds_t timeout = 0; // milliseconds
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time_t defend = 0;
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unsigned conflicts = 0;
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unsigned nprobes = 0;
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unsigned nclaims = 0;
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int t;
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int state = PROBE;
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// parse commandline: prog [options] ifname script
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while ((t = getopt(argc, argv, "fqr:v")) != EOF) {
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@ -307,6 +312,9 @@ fail:
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fds[0].events = POLLIN;
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fds[0].revents = 0;
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int source_ip_conflict = 0;
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int target_ip_conflict = 0;
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// poll, being ready to adjust current timeout
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if (!timeout) {
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timeout = ms_rdelay(PROBE_WAIT);
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@ -314,6 +322,7 @@ fail:
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// make the kernel filter out all packets except
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// ones we'd care about.
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}
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// set tv1 to the point in time when we timeout
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gettimeofday(&tv1, NULL);
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tv1.tv_usec += (timeout % 1000) * 1000;
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while (tv1.tv_usec > 1000000) {
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@ -326,64 +335,113 @@ fail:
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timeout, intf, nprobes, nclaims);
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switch (poll(fds, 1, timeout)) {
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// timeouts trigger protocol transitions
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// timeout
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case 0:
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// probes
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if (nprobes < PROBE_NUM) {
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nprobes++;
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VDBG("probe/%d %s@%s\n",
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nprobes, intf, inet_ntoa(ip));
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(void)arp(fd, &saddr, ARPOP_REQUEST,
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&addr, null_ip,
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&null_addr, ip);
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VDBG("state = %d\n", state);
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switch (state) {
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case PROBE:
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// timeouts in the PROBE state means no conflicting ARP packets
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// have been received, so we can progress through the states
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if (nprobes < PROBE_NUM) {
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nprobes++;
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VDBG("probe/%d %s@%s\n",
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nprobes, intf, inet_ntoa(ip));
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(void)arp(fd, &saddr, ARPOP_REQUEST,
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&addr, null_ip,
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&null_addr, ip);
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timeout = PROBE_MIN * 1000;
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timeout += ms_rdelay(PROBE_MAX
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- PROBE_MIN);
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} else
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timeout = ANNOUNCE_WAIT * 1000;
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}
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// then announcements
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else if (nclaims < ANNOUNCE_NUM) {
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nclaims++;
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}
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else {
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// Switch to announce state.
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state = ANNOUNCE;
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nclaims = 0;
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VDBG("announce/%d %s@%s\n",
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nclaims, intf, inet_ntoa(ip));
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(void)arp(fd, &saddr, ARPOP_REQUEST,
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&addr, ip,
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&addr, ip);
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timeout = ANNOUNCE_INTERVAL * 1000;
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}
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break;
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case RATE_LIMIT_PROBE:
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// timeouts in the RATE_LIMIT_PROBE state means no conflicting ARP packets
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// have been received, so we can move immediately to the announce state
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state = ANNOUNCE;
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nclaims = 0;
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VDBG("announce/%d %s@%s\n",
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nclaims, intf, inet_ntoa(ip));
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(void)arp(fd, &saddr, ARPOP_REQUEST,
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&addr, ip,
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&addr, ip);
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timeout = ANNOUNCE_INTERVAL * 1000;
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break;
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case ANNOUNCE:
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// timeouts in the ANNOUNCE state means no conflicting ARP packets
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// have been received, so we can progress through the states
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if (nclaims < ANNOUNCE_NUM) {
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nclaims++;
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VDBG("announce/%d %s@%s\n",
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nclaims, intf, inet_ntoa(ip));
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(void)arp(fd, &saddr, ARPOP_REQUEST,
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&addr, ip,
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&addr, ip);
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timeout = ANNOUNCE_INTERVAL * 1000;
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} else {
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}
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else {
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// Switch to monitor state.
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state = MONITOR;
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// link is ok to use earlier
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// FIXME update filters
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run(script, "config", intf, &ip);
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ready = 1;
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conflicts = 0;
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timeout = -1;
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timeout = -1; // Never timeout in the monitor state.
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// NOTE: all other exit paths
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// should deconfig ...
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if (quit)
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return EXIT_SUCCESS;
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// FIXME update filters
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}
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}
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break;
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break;
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case DEFEND:
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// We won! No ARP replies, so just go back to monitor.
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state = MONITOR;
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timeout = -1;
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conflicts = 0;
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break;
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default:
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// Invalid, should never happen. Restart the whole protocol.
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state = PROBE;
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pick(&ip);
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timeout = 0;
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nprobes = 0;
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nclaims = 0;
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break;
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} // switch (state)
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break; // case 0 (timeout)
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// packets arriving
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case 1:
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// maybe adjust timeout
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// We need to adjust the timeout in case we didn't receive
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// a conflicting packet.
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if (timeout > 0) {
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struct timeval tv2;
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gettimeofday(&tv2, NULL);
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if (timercmp(&tv1, &tv2, <)) {
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// Current time is greater than the expected timeout time.
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// Should never happen.
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VDBG("missed an expected timeout\n");
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timeout = 0;
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} else {
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VDBG("adjusting timeout\n");
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timersub(&tv1, &tv2, &tv1);
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timeout = 1000 * tv1.tv_sec
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+ tv1.tv_usec / 1000;
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}
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}
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if ((fds[0].revents & POLLIN) == 0) {
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if (fds[0].revents & POLLERR) {
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// FIXME: links routinely go down;
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@ -397,6 +455,7 @@ fail:
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}
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continue;
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}
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// read ARP packet
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if (recv(fd, &p, sizeof (p), 0) < 0) {
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why = "recv";
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@ -405,71 +464,102 @@ fail:
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if (p.hdr.ether_type != htons(ETHERTYPE_ARP))
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continue;
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VDBG("%s recv arp type=%d, op=%d,\n",
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#ifdef DEBUG
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{
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struct ether_addr * sha = (struct ether_addr *) p.arp.arp_sha;
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struct ether_addr * tha = (struct ether_addr *) p.arp.arp_tha;
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struct in_addr * spa = (struct in_addr *) p.arp.arp_spa;
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struct in_addr * tpa = (struct in_addr *) p.arp.arp_tpa;
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VDBG("%s recv arp type=%d, op=%d,\n",
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intf, ntohs(p.hdr.ether_type),
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ntohs(p.arp.ar_op));
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VDBG("\tsource=%s %s\n",
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ether_ntoa(&p.source_addr),
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inet_ntoa(p.source_ip));
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VDBG("\ttarget=%s %s\n",
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ether_ntoa(&p.target_addr),
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inet_ntoa(p.target_ip));
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if (p.arp.ar_op != htons(ARPOP_REQUEST)
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&& p.arp.ar_op != htons(ARPOP_REPLY))
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ntohs(p.arp.arp_op));
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VDBG("\tsource=%s %s\n",
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ether_ntoa(sha),
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inet_ntoa(*spa));
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VDBG("\ttarget=%s %s\n",
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ether_ntoa(tha),
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inet_ntoa(*tpa));
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}
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#endif
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if (p.arp.arp_op != htons(ARPOP_REQUEST)
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&& p.arp.arp_op != htons(ARPOP_REPLY))
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continue;
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// some cases are always conflicts
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if ((p.source_ip.s_addr == ip.s_addr)
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&& (memcmp(&addr, &p.source_addr,
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ETH_ALEN) != 0)) {
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collision:
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VDBG("%s ARP conflict from %s\n", intf,
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ether_ntoa(&p.source_addr));
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if (ready) {
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time_t now = time(0);
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if (memcmp(p.arp.arp_spa, &ip.s_addr, sizeof(struct in_addr)) == 0 &&
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memcmp(&addr, &p.arp.arp_sha, ETH_ALEN) != 0) {
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source_ip_conflict = 1;
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}
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if (memcmp(p.arp.arp_tpa, &ip.s_addr, sizeof(struct in_addr)) == 0 &&
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p.arp.arp_op == htons(ARPOP_REQUEST) &&
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memcmp(&addr, &p.arp.arp_tha, ETH_ALEN) != 0) {
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target_ip_conflict = 1;
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}
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if ((defend + DEFEND_INTERVAL)
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< now) {
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defend = now;
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(void)arp(fd, &saddr,
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ARPOP_REQUEST,
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&addr, ip,
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&addr, ip);
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VDBG("%s defend\n", intf);
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timeout = -1;
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continue;
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VDBG("state = %d, source ip conflict = %d, target ip conflict = %d\n",
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state, source_ip_conflict, target_ip_conflict);
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switch (state) {
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case PROBE:
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case ANNOUNCE:
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// When probing or announcing, check for source IP conflicts
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// and other hosts doing ARP probes (target IP conflicts).
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if (source_ip_conflict || target_ip_conflict) {
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conflicts++;
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if (conflicts >= MAX_CONFLICTS) {
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VDBG("%s ratelimit\n", intf);
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timeout = RATE_LIMIT_INTERVAL * 1000;
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state = RATE_LIMIT_PROBE;
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}
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defend = now;
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// restart the whole protocol
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pick(&ip);
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timeout = 0;
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nprobes = 0;
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nclaims = 0;
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}
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break;
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case MONITOR:
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// If a conflict, we try to defend with a single ARP probe.
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if (source_ip_conflict) {
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VDBG("monitor conflict -- defending\n");
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state = DEFEND;
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timeout = DEFEND_INTERVAL * 1000;
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(void)arp(fd, &saddr,
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ARPOP_REQUEST,
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&addr, ip,
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&addr, ip);
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}
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break;
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case DEFEND:
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// Well, we tried. Start over (on conflict).
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if (source_ip_conflict) {
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state = PROBE;
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VDBG("defend conflict -- starting over\n");
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ready = 0;
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run(script, "deconfig", intf, &ip);
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// FIXME rm filters: setsockopt(fd,
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// SO_DETACH_FILTER, ...)
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// restart the whole protocol
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pick(&ip);
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timeout = 0;
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nprobes = 0;
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nclaims = 0;
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}
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conflicts++;
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if (conflicts >= MAX_CONFLICTS) {
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VDBG("%s ratelimit\n", intf);
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sleep(RATE_LIMIT_INTERVAL);
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}
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// restart the whole protocol
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break;
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default:
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// Invalid, should never happen. Restart the whole protocol.
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VDBG("invalid state -- starting over\n");
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state = PROBE;
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pick(&ip);
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timeout = 0;
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nprobes = 0;
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nclaims = 0;
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}
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// two hosts probing one address is a collision too
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else if (p.target_ip.s_addr == ip.s_addr
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&& nclaims == 0
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&& p.arp.ar_op == htons(ARPOP_REQUEST)
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&& memcmp(&addr, &p.target_addr,
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ETH_ALEN) != 0) {
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goto collision;
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}
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break;
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break;
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} // switch state
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break; // case 1 (packets arriving)
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default:
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why = "poll";
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goto bad;
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}
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} // switch poll
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}
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bad:
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if (foreground)
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