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16aa7a73c

Denys Vlasenko
Denys Vlasenko
2015-08-04
SUCCESS Duration: 259s

Subject

zcip: simplify code

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Architecture & Compiler Flags

Architecture: x86_64-linux-gnu Compiler: gcc (Ubuntu 11.4.0-1ubuntu1~22.04.3) 11.4.0

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Commit Diff GitHub →

networking/zcip.c +96 -139
networking/zcip.c+96 -139
@@ -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 &eth_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 (&eth_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(&eth_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 *)&eth_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, */
- /* &eth_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, */
- /* &eth_addr, */ ip,
- &eth_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, */
- /* &eth_addr, */ ip,
- &eth_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, */
- /* &eth_addr, */ ip,
- &eth_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, &eth_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, */
- /* &eth_addr, */ ip,
- &eth_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