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e34758383

Denys Vlasenko
Denys Vlasenko
2015-08-04
SUCCESS Duration: 262s

Subject

zcip: another code shrink

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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 +148 -159
networking/zcip.c+148 -159
@@ -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
}