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zcip: another code shrink

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function                                             old     new   delta
send_arp_request                                       -     185    +185
zcip_main                                           1273    1272      -1
pick_nip                                              40       -     -40
arp                                                  185       -    -185
------------------------------------------------------------------------------
(add/remove: 1/2 grow/shrink: 0/1 up/down: 185/-226)          Total: -41 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2015-08-04 14:30:31 +02:00
parent 99e30be38b
commit e347583835
1 changed files with 148 additions and 159 deletions
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307
networking/zcip.c
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@ -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)
continue;
}
}
// 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;
// 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 ((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);
}
VDBG("adjusting timeout\n");
timeout_ms = (diff / 1000) | 1; // never 0
return EXIT_FAILURE;
}
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);
}
// 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;
}
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;
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;
}
}
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);
chosen_nip = pick_nip();
nsent = 0;
state = PROBE;
break;
}
// 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);
// 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;
}
// restart the whole protocol
timeout_ms = 0;
chosen_nip = pick_nip();
nsent = 0;
state = 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
}