diff options
| -rw-r--r-- | networking/zcip.c | 307 |
1 files changed, 148 insertions, 159 deletions
diff --git a/networking/zcip.c b/networking/zcip.c index 5877a83..a167c7e 100644 --- a/networking/zcip.c +++ b/networking/zcip.c @@ -90,7 +90,7 @@ enum { struct globals { struct sockaddr iface_sockaddr; - struct ether_addr eth_addr; + struct ether_addr our_ethaddr; uint32_t localnet_ip; } FIX_ALIASING; #define G (*(struct globals*)&bb_common_bufsiz1) @@ -121,14 +121,14 @@ static const char *nip_to_a(uint32_t nip) /** * Broadcast an ARP packet. */ -static void arp( +static void send_arp_request( /* int op, - always ARPOP_REQUEST */ - /* const struct ether_addr *source_eth, - always &G.eth_addr */ + /* const struct ether_addr *source_eth, - always &G.our_ethaddr */ uint32_t source_nip, const struct ether_addr *target_eth, uint32_t target_nip) { enum { op = ARPOP_REQUEST }; -#define source_eth (&G.eth_addr) +#define source_eth (&G.our_ethaddr) struct arp_packet p; memset(&p, 0, sizeof(p)); @@ -205,35 +205,34 @@ static ALWAYS_INLINE unsigned random_delay_ms(unsigned secs) int zcip_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; int zcip_main(int argc UNUSED_PARAM, char **argv) { - int state; char *r_opt; const char *l_opt = "169.254.0.0"; + int state; + int nsent; unsigned opts; - // ugly trick, but I want these zeroed in one go + // Ugly trick, but I want these zeroed in one go struct { - const struct ether_addr null_addr; + const struct ether_addr null_ethaddr; struct ifreq ifr; uint32_t chosen_nip; + int conflicts; int timeout_ms; // must be signed - unsigned conflicts; - unsigned nsent; int verbose; } L; -#define null_addr (L.null_addr ) -#define ifr (L.ifr ) -#define chosen_nip (L.chosen_nip) -#define timeout_ms (L.timeout_ms) -#define conflicts (L.conflicts ) -#define nsent (L.nsent ) -#define verbose (L.verbose ) +#define null_ethaddr (L.null_ethaddr) +#define ifr (L.ifr ) +#define chosen_nip (L.chosen_nip ) +#define conflicts (L.conflicts ) +#define timeout_ms (L.timeout_ms ) +#define verbose (L.verbose ) memset(&L, 0, sizeof(L)); INIT_G(); #define FOREGROUND (opts & 1) #define QUIT (opts & 2) - // parse commandline: prog [options] ifname script + // Parse commandline: prog [options] ifname script // exactly 2 args; -v accumulates and implies -f opt_complementary = "=2:vv:vf"; opts = getopt32(argv, "fqr:l:v", &r_opt, &l_opt, &verbose); @@ -242,7 +241,7 @@ int zcip_main(int argc UNUSED_PARAM, char **argv) if (!FOREGROUND) bb_daemonize_or_rexec(0 /*was: DAEMON_CHDIR_ROOT*/, argv); #endif - // open an ARP socket + // Open an ARP socket // (need to do it before openlog to prevent openlog from taking // fd 3 (sock_fd==3)) xmove_fd(xsocket(AF_PACKET, SOCK_PACKET, htons(ETH_P_ARP)), sock_fd); @@ -282,26 +281,26 @@ int zcip_main(int argc UNUSED_PARAM, char **argv) xsetenv("interface", argv_intf); - // initialize the interface (modprobe, ifup, etc) + // Initialize the interface (modprobe, ifup, etc) if (run(argv, "init", 0)) return EXIT_FAILURE; - // initialize G.iface_sockaddr + // Initialize G.iface_sockaddr // G.iface_sockaddr is: { u16 sa_family; u8 sa_data[14]; } //memset(&G.iface_sockaddr, 0, sizeof(G.iface_sockaddr)); //TODO: are we leaving sa_family == 0 (AF_UNSPEC)?! safe_strncpy(G.iface_sockaddr.sa_data, argv_intf, sizeof(G.iface_sockaddr.sa_data)); - // bind to the interface's ARP socket + // Bind to the interface's ARP socket xbind(sock_fd, &G.iface_sockaddr, sizeof(G.iface_sockaddr)); - // get the interface's ethernet address + // Get the interface's ethernet address //memset(&ifr, 0, sizeof(ifr)); strncpy_IFNAMSIZ(ifr.ifr_name, argv_intf); xioctl(sock_fd, SIOCGIFHWADDR, &ifr); - memcpy(&G.eth_addr, &ifr.ifr_hwaddr.sa_data, ETH_ALEN); + memcpy(&G.our_ethaddr, &ifr.ifr_hwaddr.sa_data, ETH_ALEN); - // start with some stable ip address, either a function of + // Start with some stable ip address, either a function of // the hardware address or else the last address we used. // we are taking low-order four bytes, as top-order ones // aren't random enough. @@ -309,17 +308,14 @@ int zcip_main(int argc UNUSED_PARAM, char **argv) // depending on when we detect conflicts. { uint32_t t; - move_from_unaligned32(t, ((char *)&G.eth_addr + 2)); + move_from_unaligned32(t, ((char *)&G.our_ethaddr + 2)); srand(t); } - if (chosen_nip == 0) - chosen_nip = pick_nip(); - // FIXME cases to handle: // - zcip already running! // - link already has local address... just defend/update - // daemonize now; don't delay system startup + // Daemonize now; don't delay system startup if (!FOREGROUND) { #if BB_MMU bb_daemonize(0 /*was: DAEMON_CHDIR_ROOT*/); @@ -327,14 +323,14 @@ int zcip_main(int argc UNUSED_PARAM, char **argv) bb_info_msg("start, interface %s", argv_intf); } - // run the dynamic address negotiation protocol, + // Run the dynamic address negotiation protocol, // restarting after address conflicts: // - start with some address we want to try // - short random delay // - arp probes to see if another host uses it - // 00:04:e2:64:23:c2 > ff:ff:ff:ff:ff:ff, ARP (0x0806): arp who-has 169.254.194.171 tell 0.0.0.0 + // 00:04:e2:64:23:c2 > ff:ff:ff:ff:ff:ff: arp who-has 169.254.194.171 tell 0.0.0.0 // - arp announcements that we're claiming it - // 00:04:e2:64:23:c2 > ff:ff:ff:ff:ff:ff, ARP (0x0806): arp who-has 169.254.194.171 (00:04:e2:64:23:c2) tell 169.254.194.171 + // 00:04:e2:64:23:c2 > ff:ff:ff:ff:ff:ff: arp who-has 169.254.194.171 (00:04:e2:64:23:c2) tell 169.254.194.171 // - use it // - defend it, within limits // exit if: @@ -342,73 +338,73 @@ int zcip_main(int argc UNUSED_PARAM, char **argv) // run "<script> config", then exit with exitcode 0 // - poll error (when does this happen?) // - read error (when does this happen?) - // - sendto error (in arp()) (when does this happen?) + // - sendto error (in send_arp_request()) (when does this happen?) // - revents & POLLERR (link down). run "<script> deconfig" first + if (chosen_nip == 0) { + new_nip_and_PROBE: + chosen_nip = pick_nip(); + } + nsent = 0; state = PROBE; while (1) { struct pollfd fds[1]; unsigned deadline_us; struct arp_packet p; int ip_conflict; + int n; fds[0].fd = sock_fd; fds[0].events = POLLIN; fds[0].revents = 0; - // poll, being ready to adjust current timeout + // Poll, being ready to adjust current timeout if (!timeout_ms) { timeout_ms = random_delay_ms(PROBE_WAIT); // FIXME setsockopt(sock_fd, SO_ATTACH_FILTER, ...) to // make the kernel filter out all packets except // ones we'd care about. } - // set deadline_us to the point in time when we timeout + // Set deadline_us to the point in time when we timeout deadline_us = MONOTONIC_US() + timeout_ms * 1000; VDBG("...wait %d %s nsent=%u\n", timeout_ms, argv_intf, nsent); - switch (safe_poll(fds, 1, timeout_ms)) { - - default: + n = safe_poll(fds, 1, timeout_ms); + if (n < 0) { //bb_perror_msg("poll"); - done in safe_poll return EXIT_FAILURE; - - // timeout - case 0: - VDBG("state = %d\n", state); + } + if (n == 0) { // timed out? + VDBG("state:%d\n", state); switch (state) { case PROBE: - // timeouts in the PROBE state mean no conflicting ARP packets - // have been received, so we can progress through the states + // No conflicting ARP packets were seen: + // we can progress through the states if (nsent < PROBE_NUM) { nsent++; VDBG("probe/%u %s@%s\n", nsent, argv_intf, nip_to_a(chosen_nip)); timeout_ms = PROBE_MIN * 1000; timeout_ms += random_delay_ms(PROBE_MAX - PROBE_MIN); - arp(/* ARPOP_REQUEST, */ - /* &G.eth_addr, */ 0, - &null_addr, chosen_nip); - break; + send_arp_request(0, &null_ethaddr, chosen_nip); + continue; } // Switch to announce state nsent = 0; state = ANNOUNCE; goto send_announce; case ANNOUNCE: - // timeouts in the ANNOUNCE state mean no conflicting ARP packets - // have been received, so we can progress through the states + // No conflicting ARP packets were seen: + // we can progress through the states if (nsent < ANNOUNCE_NUM) { send_announce: nsent++; VDBG("announce/%u %s@%s\n", nsent, argv_intf, nip_to_a(chosen_nip)); timeout_ms = ANNOUNCE_INTERVAL * 1000; - arp(/* ARPOP_REQUEST, */ - /* &G.eth_addr, */ chosen_nip, - &G.eth_addr, chosen_nip); - break; + send_arp_request(chosen_nip, &G.our_ethaddr, chosen_nip); + continue; } // Switch to monitor state // FIXME update filters @@ -416,124 +412,117 @@ int zcip_main(int argc UNUSED_PARAM, char **argv) // NOTE: all other exit paths should deconfig... if (QUIT) return EXIT_SUCCESS; - conflicts = 0; - timeout_ms = -1; // Never timeout in the monitor state. - state = MONITOR; - break; - case DEFEND: + // fall through: switch_to_MONITOR + default: + // case DEFEND: + // case MONITOR: (shouldn't happen, MONITOR timeout is infinite) // Defend period ended with no ARP replies - we won - conflicts = 0; - timeout_ms = -1; + timeout_ms = -1; // never timeout in monitor state state = MONITOR; - break; - } // switch (state) - break; // case 0 (timeout) - - // packets arriving, or link went down - case 1: - // We need to adjust the timeout in case we didn't receive - // a conflicting packet. - if (timeout_ms > 0) { - unsigned diff = deadline_us - MONOTONIC_US(); - if ((int)(diff) < 0) { - // Current time is greater than the expected timeout time. - diff = 0; - } - VDBG("adjusting timeout\n"); - timeout_ms = (diff / 1000) | 1; // never 0 - } - - if ((fds[0].revents & POLLIN) == 0) { - if (fds[0].revents & POLLERR) { - // FIXME: links routinely go down; - // this shouldn't necessarily exit. - bb_error_msg("iface %s is down", argv_intf); - if (state >= MONITOR) { - // only if we are in MONITOR or DEFEND - run(argv, "deconfig", chosen_nip); - } - return EXIT_FAILURE; - } continue; } + } - // read ARP packet - if (safe_read(sock_fd, &p, sizeof(p)) < 0) { - bb_perror_msg_and_die(bb_msg_read_error); + // Packet arrived, or link went down. + // We need to adjust the timeout in case we didn't receive + // a conflicting packet. + if (timeout_ms > 0) { + unsigned diff = deadline_us - MONOTONIC_US(); + if ((int)(diff) < 0) { + // Current time is greater than the expected timeout time. + diff = 0; } + VDBG("adjusting timeout\n"); + timeout_ms = (diff / 1000) | 1; // never 0 + } - if (p.eth.ether_type != htons(ETHERTYPE_ARP)) - continue; - if (p.arp.arp_op != htons(ARPOP_REQUEST) - && p.arp.arp_op != htons(ARPOP_REPLY) - ) { - continue; + if ((fds[0].revents & POLLIN) == 0) { + if (fds[0].revents & POLLERR) { + // FIXME: links routinely go down; + // this shouldn't necessarily exit. + bb_error_msg("iface %s is down", argv_intf); + if (state >= MONITOR) { + // Only if we are in MONITOR or DEFEND + run(argv, "deconfig", chosen_nip); + } + return EXIT_FAILURE; } + continue; + } + + // Read ARP packet + if (safe_read(sock_fd, &p, sizeof(p)) < 0) { + bb_perror_msg_and_die(bb_msg_read_error); + } + + if (p.eth.ether_type != htons(ETHERTYPE_ARP)) + continue; + if (p.arp.arp_op != htons(ARPOP_REQUEST) + && p.arp.arp_op != htons(ARPOP_REPLY) + ) { + continue; + } #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("source=%s %s\n", ether_ntoa(sha), inet_ntoa(*spa)); - VDBG("target=%s %s\n", ether_ntoa(tha), inet_ntoa(*tpa)); - } + { + 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("source=%s %s\n", ether_ntoa(sha), inet_ntoa(*spa)); + VDBG("target=%s %s\n", ether_ntoa(tha), inet_ntoa(*tpa)); + } #endif - ip_conflict = 0; - if (memcmp(&p.arp.arp_sha, &G.eth_addr, ETH_ALEN) != 0) { - if (memcmp(p.arp.arp_spa, &chosen_nip, 4) == 0) { - // A probe or reply with source_ip == chosen ip - ip_conflict = 1; - } - if (p.arp.arp_op == htons(ARPOP_REQUEST) - && memcmp(p.arp.arp_spa, &const_int_0, 4) == 0 - && memcmp(p.arp.arp_tpa, &chosen_nip, 4) == 0 - ) { - // A probe with source_ip == 0.0.0.0, target_ip == chosen ip: - // another host trying to claim this ip! - ip_conflict |= 2; - } + ip_conflict = 0; + if (memcmp(&p.arp.arp_sha, &G.our_ethaddr, ETH_ALEN) != 0) { + if (memcmp(p.arp.arp_spa, &chosen_nip, 4) == 0) { + // A probe or reply with source_ip == chosen ip + ip_conflict = 1; } - VDBG("state:%d ip_conflict:%d\n", state, ip_conflict); - if (!ip_conflict) - break; - - // Either src or target IP conflict exists - if (state <= ANNOUNCE) { - // PROBE or ANNOUNCE - conflicts++; - timeout_ms = PROBE_MIN * 1000 - + CONFLICT_MULTIPLIER * random_delay_ms(conflicts); - chosen_nip = pick_nip(); - nsent = 0; - state = PROBE; - break; + if (p.arp.arp_op == htons(ARPOP_REQUEST) + && memcmp(p.arp.arp_spa, &const_int_0, 4) == 0 + && memcmp(p.arp.arp_tpa, &chosen_nip, 4) == 0 + ) { + // A probe with source_ip == 0.0.0.0, target_ip == chosen ip: + // another host trying to claim this ip! + ip_conflict |= 2; } - // MONITOR or DEFEND: only src IP conflict is a problem - if (ip_conflict & 1) { - if (state == MONITOR) { - // Src IP conflict, defend with a single ARP probe - VDBG("monitor conflict - defending\n"); - timeout_ms = DEFEND_INTERVAL * 1000; - state = DEFEND; - arp(/* ARPOP_REQUEST, */ - /* &G.eth_addr, */ chosen_nip, - &G.eth_addr, chosen_nip); - break; - } - // state == DEFEND - // Another src IP conflict, start over - VDBG("defend conflict - starting over\n"); - run(argv, "deconfig", chosen_nip); - - // restart the whole protocol - timeout_ms = 0; - chosen_nip = pick_nip(); - nsent = 0; - state = PROBE; + } + VDBG("state:%d ip_conflict:%d\n", state, ip_conflict); + if (!ip_conflict) + continue; + + // Either src or target IP conflict exists + if (state <= ANNOUNCE) { + // PROBE or ANNOUNCE + conflicts++; + timeout_ms = PROBE_MIN * 1000 + + CONFLICT_MULTIPLIER * random_delay_ms(conflicts); + goto new_nip_and_PROBE; + } + + // MONITOR or DEFEND: only src IP conflict is a problem + if (ip_conflict & 1) { + if (state == MONITOR) { + // Src IP conflict, defend with a single ARP probe + VDBG("monitor conflict - defending\n"); + timeout_ms = DEFEND_INTERVAL * 1000; + state = DEFEND; + send_arp_request(chosen_nip, &G.our_ethaddr, chosen_nip); + continue; } - break; // case 1 (packet arrived) - } // switch (poll) + // state == DEFEND + // Another src IP conflict, start over + VDBG("defend conflict - starting over\n"); + run(argv, "deconfig", chosen_nip); + conflicts = 0; + timeout_ms = 0; + goto new_nip_and_PROBE; + } + // Note: if we only have a target IP conflict here (ip_conflict & 2), + // IOW: if we just saw this sort of ARP packet: + // aa:bb:cc:dd:ee:ff > xx:xx:xx:xx:xx:xx: arp who-has <chosen_nip> tell 0.0.0.0 + // we expect _kernel_ to respond to that, because <chosen_nip> + // is (expected to be) configured on this iface. } // while (1) #undef argv_intf } |