From: Denys Vlasenko Date: Tue, 4 Aug 2015 01:27:56 +0000 (+0200) Subject: zcip: simplify code X-Git-Tag: 1_24_0~74 X-Git-Url: https://git.librecmc.org/?a=commitdiff_plain;h=16aa7a73c40ba5dfaabaedb8a5533619cb8b6cb6;p=oweals%2Fbusybox.git zcip: simplify code function old new delta zcip_main 1411 1263 -148 Signed-off-by: Denys Vlasenko --- diff --git a/networking/zcip.c b/networking/zcip.c index 962ba2e60..69644b230 100644 --- a/networking/zcip.c +++ b/networking/zcip.c @@ -56,26 +56,26 @@ struct arp_packet { } PACKED; enum { -/* 169.254.0.0 */ + /* 169.254.0.0 */ LINKLOCAL_ADDR = 0xa9fe0000, -/* protocol timeout parameters, specified in seconds */ + /* 0-1 seconds before sending 1st probe */ PROBE_WAIT = 1, + /* 1-2 seconds between probes */ PROBE_MIN = 1, PROBE_MAX = 2, - PROBE_NUM = 3, - MAX_CONFLICTS = 10, - RATE_LIMIT_INTERVAL = 60, - ANNOUNCE_WAIT = 2, - ANNOUNCE_NUM = 2, - ANNOUNCE_INTERVAL = 2, + PROBE_NUM = 3, /* total probes to send */ + ANNOUNCE_INTERVAL = 2, /* 2 seconds between announces */ + ANNOUNCE_NUM = 3, /* announces to send */ + /* if probe/announce sees a conflict, multiply RANDOM(NUM_CONFLICT) by... */ + CONFLICT_MULTIPLIER = 2, + /* if we monitor and see a conflict, how long is defend state? */ DEFEND_INTERVAL = 10 }; /* States during the configuration process. */ enum { PROBE = 0, - RATE_LIMIT_PROBE, ANNOUNCE, MONITOR, DEFEND @@ -89,13 +89,11 @@ enum { }; struct globals { - struct sockaddr saddr; + struct sockaddr iface_sockaddr; struct ether_addr eth_addr; uint32_t localnet_ip; } FIX_ALIASING; #define G (*(struct globals*)&bb_common_bufsiz1) -#define saddr (G.saddr ) -#define eth_addr (G.eth_addr) #define INIT_G() do { } while (0) @@ -113,17 +111,24 @@ static uint32_t pick_nip(void) return htonl((G.localnet_ip + 0x0100) + tmp); } +static const char *nip_to_a(uint32_t nip) +{ + struct in_addr in; + in.s_addr = nip; + return inet_ntoa(in); +} + /** * Broadcast an ARP packet. */ static void arp( /* int op, - always ARPOP_REQUEST */ - /* const struct ether_addr *source_eth, - always ð_addr */ - struct in_addr source_ip, - const struct ether_addr *target_eth, struct in_addr target_ip) + /* const struct ether_addr *source_eth, - always &G.eth_addr */ + uint32_t source_nip, + const struct ether_addr *target_eth, uint32_t target_nip) { enum { op = ARPOP_REQUEST }; -#define source_eth (ð_addr) +#define source_eth (&G.eth_addr) struct arp_packet p; memset(&p, 0, sizeof(p)); @@ -140,18 +145,18 @@ static void arp( p.arp.arp_pln = 4; p.arp.arp_op = htons(op); memcpy(&p.arp.arp_sha, source_eth, ETH_ALEN); - memcpy(&p.arp.arp_spa, &source_ip, sizeof(p.arp.arp_spa)); + memcpy(&p.arp.arp_spa, &source_nip, 4); memcpy(&p.arp.arp_tha, target_eth, ETH_ALEN); - memcpy(&p.arp.arp_tpa, &target_ip, sizeof(p.arp.arp_tpa)); + memcpy(&p.arp.arp_tpa, &target_nip, 4); // send it - // Even though sock_fd is already bound to saddr, just send() + // Even though sock_fd is already bound to G.iface_sockaddr, just send() // won't work, because "socket is not connected" // (and connect() won't fix that, "operation not supported"). - // Thus we sendto() to saddr. I wonder which sockaddr + // Thus we sendto() to G.iface_sockaddr. I wonder which sockaddr // (from bind() or from sendto()?) kernel actually uses // to determine iface to emit the packet from... - xsendto(sock_fd, &p, sizeof(p), &saddr, sizeof(saddr)); + xsendto(sock_fd, &p, sizeof(p), &G.iface_sockaddr, sizeof(G.iface_sockaddr)); #undef source_eth } @@ -159,18 +164,18 @@ static void arp( * Run a script. * argv[0]:intf argv[1]:script_name argv[2]:junk argv[3]:NULL */ -static int run(char *argv[3], const char *param, struct in_addr *ip) +static int run(char *argv[3], const char *param, uint32_t nip) { int status; - char *addr = addr; /* for gcc */ + const char *addr = addr; /* for gcc */ const char *fmt = "%s %s %s" + 3; argv[2] = (char*)param; VDBG("%s run %s %s\n", argv[0], argv[1], argv[2]); - if (ip) { - addr = inet_ntoa(*ip); + if (nip != 0) { + addr = nip_to_a(nip); xsetenv("ip", addr); fmt -= 3; } @@ -207,26 +212,22 @@ int zcip_main(int argc UNUSED_PARAM, char **argv) // ugly trick, but I want these zeroed in one go struct { - const struct in_addr null_ip; const struct ether_addr null_addr; - struct in_addr ip; struct ifreq ifr; + uint32_t chosen_nip; int timeout_ms; /* must be signed */ unsigned conflicts; unsigned nprobes; unsigned nclaims; - int ready; int verbose; } L; -#define null_ip (L.null_ip ) #define null_addr (L.null_addr ) -#define ip (L.ip ) +#define chosen_nip (L.chosen_nip) #define ifr (L.ifr ) #define timeout_ms (L.timeout_ms) #define conflicts (L.conflicts ) #define nprobes (L.nprobes ) #define nclaims (L.nclaims ) -#define ready (L.ready ) #define verbose (L.verbose ) memset(&L, 0, sizeof(L)); @@ -264,11 +265,13 @@ int zcip_main(int argc UNUSED_PARAM, char **argv) G.localnet_ip = ntohl(net.s_addr); } if (opts & 4) { // -r n.n.n.n + struct in_addr ip; if (inet_aton(r_opt, &ip) == 0 || (ntohl(ip.s_addr) & IN_CLASSB_NET) != G.localnet_ip ) { bb_error_msg_and_die("invalid link address"); } + chosen_nip = ip.s_addr; } argv += optind - 1; @@ -282,23 +285,23 @@ int zcip_main(int argc UNUSED_PARAM, char **argv) xsetenv("interface", argv_intf); // initialize the interface (modprobe, ifup, etc) - if (run(argv, "init", NULL)) + if (run(argv, "init", 0)) return EXIT_FAILURE; - // initialize saddr - // saddr is: { u16 sa_family; u8 sa_data[14]; } - //memset(&saddr, 0, sizeof(saddr)); + // 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(saddr.sa_data, argv_intf, sizeof(saddr.sa_data)); + safe_strncpy(G.iface_sockaddr.sa_data, argv_intf, sizeof(G.iface_sockaddr.sa_data)); // bind to the interface's ARP socket - xbind(sock_fd, &saddr, sizeof(saddr)); + xbind(sock_fd, &G.iface_sockaddr, sizeof(G.iface_sockaddr)); // get the interface's ethernet address //memset(&ifr, 0, sizeof(ifr)); strncpy_IFNAMSIZ(ifr.ifr_name, argv_intf); xioctl(sock_fd, SIOCGIFHWADDR, &ifr); - memcpy(ð_addr, &ifr.ifr_hwaddr.sa_data, ETH_ALEN); + memcpy(&G.eth_addr, &ifr.ifr_hwaddr.sa_data, ETH_ALEN); // start with some stable ip address, either a function of // the hardware address or else the last address we used. @@ -308,11 +311,11 @@ int zcip_main(int argc UNUSED_PARAM, char **argv) // depending on when we detect conflicts. { uint32_t t; - move_from_unaligned32(t, ((char *)ð_addr + 2)); + move_from_unaligned32(t, ((char *)&G.eth_addr + 2)); srand(t); } - if (ip.s_addr == 0) - ip.s_addr = pick_nip(); + if (chosen_nip == 0) + chosen_nip = pick_nip(); // FIXME cases to handle: // - zcip already running! @@ -331,7 +334,9 @@ int zcip_main(int argc UNUSED_PARAM, char **argv) // - 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 // - 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 // - use it // - defend it, within limits // exit if: @@ -382,78 +387,47 @@ int zcip_main(int argc UNUSED_PARAM, char **argv) if (nprobes < PROBE_NUM) { nprobes++; VDBG("probe/%u %s@%s\n", - nprobes, argv_intf, inet_ntoa(ip)); + nprobes, argv_intf, nip_to_a(chosen_nip)); timeout_ms = PROBE_MIN * 1000; timeout_ms += random_delay_ms(PROBE_MAX - PROBE_MIN); arp(/* ARPOP_REQUEST, */ - /* ð_addr, */ null_ip, - &null_addr, ip); - } - else { - // Switch to announce state. - state = ANNOUNCE; - nclaims = 0; - VDBG("announce/%u %s@%s\n", - nclaims, argv_intf, inet_ntoa(ip)); - timeout_ms = ANNOUNCE_INTERVAL * 1000; - arp(/* ARPOP_REQUEST, */ - /* ð_addr, */ ip, - ð_addr, ip); + /* &G.eth_addr, */ 0, + &null_addr, chosen_nip); + break; } - break; - case RATE_LIMIT_PROBE: - // timeouts in the RATE_LIMIT_PROBE state mean no conflicting ARP packets - // have been received, so we can move immediately to the announce state - state = ANNOUNCE; + // Switch to announce state. nclaims = 0; - VDBG("announce/%u %s@%s\n", - nclaims, argv_intf, inet_ntoa(ip)); - timeout_ms = ANNOUNCE_INTERVAL * 1000; - arp(/* ARPOP_REQUEST, */ - /* ð_addr, */ ip, - ð_addr, ip); - break; + 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 if (nclaims < ANNOUNCE_NUM) { + send_announce: nclaims++; VDBG("announce/%u %s@%s\n", - nclaims, argv_intf, inet_ntoa(ip)); + nclaims, argv_intf, nip_to_a(chosen_nip)); timeout_ms = ANNOUNCE_INTERVAL * 1000; arp(/* ARPOP_REQUEST, */ - /* ð_addr, */ ip, - ð_addr, ip); - } - else { - // Switch to monitor state. - state = MONITOR; - // link is ok to use earlier - // FIXME update filters - run(argv, "config", &ip); - ready = 1; - conflicts = 0; - timeout_ms = -1; // Never timeout in the monitor state. - - // NOTE: all other exit paths - // should deconfig ... - if (QUIT) - return EXIT_SUCCESS; + /* &G.eth_addr, */ chosen_nip, + &G.eth_addr, chosen_nip); + break; } + // Switch to monitor state. + // FIXME update filters + run(argv, "config", chosen_nip); + // 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: - // We won! No ARP replies, so just go back to monitor. - state = MONITOR; - timeout_ms = -1; + // Defend period ended with no ARP replies - we won. conflicts = 0; - break; - default: - // Invalid, should never happen. Restart the whole protocol. - state = PROBE; - ip.s_addr = pick_nip(); - timeout_ms = 0; - nprobes = 0; - nclaims = 0; + timeout_ms = -1; + state = MONITOR; break; } // switch (state) break; // case 0 (timeout) @@ -466,13 +440,10 @@ int zcip_main(int argc UNUSED_PARAM, char **argv) unsigned diff = deadline_us - MONOTONIC_US(); if ((int)(diff) < 0) { // Current time is greater than the expected timeout time. - // Should never happen. - VDBG("missed an expected timeout\n"); - timeout_ms = 0; - } else { - VDBG("adjusting timeout\n"); - timeout_ms = (diff / 1000) | 1; /* never 0 */ + diff = 0; } + VDBG("adjusting timeout\n"); + timeout_ms = (diff / 1000) | 1; /* never 0 */ } if ((fds[0].revents & POLLIN) == 0) { @@ -480,8 +451,9 @@ int zcip_main(int argc UNUSED_PARAM, char **argv) // FIXME: links routinely go down; // this shouldn't necessarily exit. bb_error_msg("iface %s is down", argv_intf); - if (ready) { - run(argv, "deconfig", &ip); + if (state >= MONITOR) { + /* only if we are in MONITOR or DEFEND */ + run(argv, "deconfig", chosen_nip); } return EXIT_FAILURE; } @@ -492,8 +464,14 @@ int zcip_main(int argc UNUSED_PARAM, char **argv) 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; @@ -511,23 +489,17 @@ int zcip_main(int argc UNUSED_PARAM, char **argv) inet_ntoa(*tpa)); } #endif - if (p.arp.arp_op != htons(ARPOP_REQUEST) - && p.arp.arp_op != htons(ARPOP_REPLY) - ) { - continue; - } - source_ip_conflict = 0; target_ip_conflict = 0; - if (memcmp(&p.arp.arp_sha, ð_addr, ETH_ALEN) != 0) { - if (memcmp(p.arp.arp_spa, &ip.s_addr, sizeof(struct in_addr)) == 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 */ source_ip_conflict = 1; } if (p.arp.arp_op == htons(ARPOP_REQUEST) - && memcmp(p.arp.arp_spa, &null_ip, sizeof(struct in_addr)) == 0 - && memcmp(p.arp.arp_tpa, &ip.s_addr, sizeof(struct in_addr)) == 0 + && 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! @@ -545,54 +517,39 @@ int zcip_main(int argc UNUSED_PARAM, char **argv) // 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", argv_intf); - timeout_ms = RATE_LIMIT_INTERVAL * 1000; - state = RATE_LIMIT_PROBE; - } - - // restart the whole protocol - ip.s_addr = pick_nip(); - timeout_ms = 0; + timeout_ms = PROBE_MIN * 1000 + + CONFLICT_MULTIPLIER * random_delay_ms(conflicts); + chosen_nip = pick_nip(); nprobes = 0; nclaims = 0; + state = PROBE; } 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_ms = DEFEND_INTERVAL * 1000; + state = DEFEND; arp(/* ARPOP_REQUEST, */ - /* ð_addr, */ ip, - ð_addr, ip); + /* &G.eth_addr, */ chosen_nip, + &G.eth_addr, chosen_nip); } 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(argv, "deconfig", &ip); + run(argv, "deconfig", chosen_nip); // restart the whole protocol - ip.s_addr = pick_nip(); timeout_ms = 0; + chosen_nip = pick_nip(); nprobes = 0; nclaims = 0; + state = PROBE; } break; - default: - // Invalid, should never happen. Restart the whole protocol. - VDBG("invalid state -- starting over\n"); - state = PROBE; - ip.s_addr = pick_nip(); - timeout_ms = 0; - nprobes = 0; - nclaims = 0; - break; } // switch state break; // case 1 (packets arriving) } // switch poll