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Refactor the ARP code to be similar to the dhcp code -- timeout functions and

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packet response functions are handled by an array of function pointers indexed
by ARP state.

Split arp_retransmit() apart into simpler functions.

Fix a typo in renewing_timeout() that would result in too-short timeouts that
would soak cpu.

Call handle_arp_timeout() from the timeout_action() function rather than
having
explicit hooks in various <dhcpstate>_timeout() functions.

Make the function pointer arrays static const.
This commit is contained in:
Nicholas J. Kain
2011-07-11 05:09:38 -04:00
parent 8beb1d12d1
commit 1e71f82f3a
3 changed files with 123 additions and 102 deletions
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198
ndhc/arp.c
View File

@@ -1,5 +1,5 @@
/* arp.c - arp ping checking
* Time-stamp: <2011-07-06 11:39:23 njk>
* Time-stamp: <2011-07-09 17:34:29 njk>
*
* Copyright 2010-2011 Nicholas J. Kain <njkain@gmail.com>
*
@@ -524,8 +524,7 @@ static int arp_gen_probe_wait(void)
return PROBE_MIN + rand() % (PROBE_MAX - PROBE_MIN);
}
// Perform retransmission if necessary.
void arp_retransmit(struct client_state_t *cs)
static void arp_defense_timeout(struct client_state_t *cs)
{
if (pending_def_ts) {
log_line("arp: Defending our lease IP.");
@@ -537,42 +536,48 @@ void arp_retransmit(struct client_state_t *cs)
def_old_oldTimeout = 0;
}
}
if (arpState == AS_GW_CHECK || arpState == AS_GW_QUERY) {
if (arpState == AS_GW_CHECK && act_if_arp_gw_failed(cs))
return;
long long cms = curms();
long long rtts = arp_send_stats[ASEND_GW_PING].ts + ARP_RETRANS_DELAY;
if (cms < rtts) {
cs->timeout = rtts - cms;
return;
}
log_line(arpState == AS_GW_CHECK ?
"arp: Still waiting for gateway to reply to arp ping..." :
"arp: Still looking for gateway hardware address...");
if (arp_ping(cs, cs->routerAddr) == -1)
log_warning("arp: Failed to send ARP ping in retransmission.");
cs->timeout = ARP_RETRANS_DELAY;
}
static void arp_check_timeout(struct client_state_t *cs)
{
arp_defense_timeout(cs);
if (arpState == AS_GW_CHECK && act_if_arp_gw_failed(cs))
return;
long long cms = curms();
long long rtts = arp_send_stats[ASEND_GW_PING].ts + ARP_RETRANS_DELAY;
if (cms < rtts) {
cs->timeout = rtts - cms;
return;
}
if (arpState == AS_COLLISION_CHECK) {
long long cms = curms();
if (cms >= collision_check_init_ts + ANNOUNCE_WAIT ||
arp_send_stats[ASEND_COLLISION_CHECK].count >= PROBE_NUM) {
arp_success(cs);
return;
}
long long rtts = arp_send_stats[ASEND_COLLISION_CHECK].ts +
probe_wait_time;
if (cms < rtts) {
cs->timeout = rtts - cms;
return;
}
log_line("arp: Probing for hosts that may conflict with our lease...");
if (arp_ip_anon_ping(cs, arp_dhcp_packet.yiaddr) == -1)
log_warning("arp: Failed to send ARP ping in retransmission.");
cs->timeout = probe_wait_time = arp_gen_probe_wait();
log_line(arpState == AS_GW_CHECK ?
"arp: Still waiting for gateway to reply to arp ping..." :
"arp: Still looking for gateway hardware address...");
if (arp_ping(cs, cs->routerAddr) == -1)
log_warning("arp: Failed to send ARP ping in retransmission.");
cs->timeout = ARP_RETRANS_DELAY;
}
static void arp_collision_timeout(struct client_state_t *cs)
{
arp_defense_timeout(cs);
long long cms = curms();
if (cms >= collision_check_init_ts + ANNOUNCE_WAIT ||
arp_send_stats[ASEND_COLLISION_CHECK].count >= PROBE_NUM) {
arp_success(cs);
return;
}
long long rtts = arp_send_stats[ASEND_COLLISION_CHECK].ts +
probe_wait_time;
if (cms < rtts) {
cs->timeout = rtts - cms;
return;
}
log_line("arp: Probing for hosts that may conflict with our lease...");
if (arp_ip_anon_ping(cs, arp_dhcp_packet.yiaddr) == -1)
log_warning("arp: Failed to send ARP ping in retransmission.");
cs->timeout = probe_wait_time = arp_gen_probe_wait();
}
static void arp_do_defense(struct client_state_t *cs)
@@ -600,6 +605,72 @@ static void arp_do_defense(struct client_state_t *cs)
last_conflict_ts = cur_conflict_ts;
}
static void arp_do_gw_query(struct client_state_t *cs)
{
if (arp_is_query_reply(&arpreply) &&
!memcmp(arpreply.sip4, &cs->routerAddr, 4)) {
cs->timeout = cs->oldTimeout;
memcpy(cs->routerArp, arpreply.smac, 6);
log_line("arp: Gateway hardware address %02x:%02x:%02x:%02x:%02x:%02x",
cs->routerArp[0], cs->routerArp[1],
cs->routerArp[2], cs->routerArp[3],
cs->routerArp[4], cs->routerArp[5]);
arp_switch_state(cs, AS_DEFENSE);
arp_announcement(cs); // Do a second announcement.
return;
}
if (!arp_validate_bpf_defense(cs, &arpreply))
return;
arp_do_defense(cs);
}
static void arp_do_collision_check(struct client_state_t *cs)
{
if (!arp_is_query_reply(&arpreply))
return;
// If this packet was sent from our lease IP, and does not have a
// MAC address matching our own (the latter check guards against stupid
// hubs or repeaters), then it's a conflict and thus a failure.
if (!memcmp(arpreply.sip4, &arp_dhcp_packet.yiaddr, 4) &&
!memcmp(client_config.arp, arpreply.smac, 6)) {
total_conflicts++;
arp_failed(cs);
}
}
static void arp_do_gw_check(struct client_state_t *cs)
{
if (!arp_is_query_reply(&arpreply))
return;
if (!memcmp(arpreply.sip4, &cs->routerAddr, 4)) {
// Success only if the router/gw MAC matches stored value
if (!memcmp(cs->routerArp, arpreply.smac, 6))
arp_gw_success(cs);
else
arp_gw_failed(cs);
}
}
static void arp_do_invalid(struct client_state_t *cs)
{
log_error("handle_arp_response: called in invalid state %u", arpState);
arp_close_fd(cs);
}
typedef struct {
void (*packet_fn)(struct client_state_t *cs);
void (*timeout_fn)(struct client_state_t *cs);
} arp_state_fn_t;
static const arp_state_fn_t arp_states[] = {
{ arp_do_invalid, 0 }, // AS_NONE
{ arp_do_collision_check, arp_collision_timeout }, // AS_COLLISION_CHECK
{ arp_do_gw_check, arp_check_timeout }, // AS_GW_CHECK
{ arp_do_gw_query, arp_check_timeout }, // AS_GW_QUERY
{ arp_do_defense, arp_defense_timeout }, // AS_DEFENSE
{ arp_do_invalid, 0 }, // AS_MAX
};
void handle_arp_response(struct client_state_t *cs)
{
int r = 0;
@@ -620,7 +691,7 @@ void handle_arp_response(struct client_state_t *cs)
}
if (r <= 0) {
arp_retransmit(cs);
handle_arp_timeout(cs);
return;
}
@@ -635,51 +706,14 @@ void handle_arp_response(struct client_state_t *cs)
return;
}
switch (arpState) {
case AS_COLLISION_CHECK:
if (!arp_is_query_reply(&arpreply))
break;
// If this packet was sent from our lease IP, and does not have a
// MAC address matching our own (the latter check guards against stupid
// hubs or repeaters), then it's a conflict and thus a failure.
if (!memcmp(arpreply.sip4, &arp_dhcp_packet.yiaddr, 4) &&
!memcmp(client_config.arp, arpreply.smac, 6)) {
total_conflicts++;
arp_failed(cs);
}
break;
case AS_GW_CHECK:
if (!arp_is_query_reply(&arpreply))
break;
if (!memcmp(arpreply.sip4, &cs->routerAddr, 4)) {
// Success only if the router/gw MAC matches stored value
if (!memcmp(cs->routerArp, arpreply.smac, 6))
arp_gw_success(cs);
else
arp_gw_failed(cs);
}
break;
case AS_GW_QUERY:
if (arp_is_query_reply(&arpreply) &&
!memcmp(arpreply.sip4, &cs->routerAddr, 4)) {
cs->timeout = cs->oldTimeout;
memcpy(cs->routerArp, arpreply.smac, 6);
log_line("arp: Gateway hardware address %02x:%02x:%02x:%02x:%02x:%02x",
cs->routerArp[0], cs->routerArp[1],
cs->routerArp[2], cs->routerArp[3],
cs->routerArp[4], cs->routerArp[5]);
arp_switch_state(cs, AS_DEFENSE);
arp_announcement(cs); // Do a second announcement.
break;
}
if (!arp_validate_bpf_defense(cs, &arpreply))
break;
case AS_DEFENSE:
arp_do_defense(cs);
break;
default:
log_error("handle_arp_response: called in invalid state %u", arpState);
arp_close_fd(cs);
}
if (arp_states[arpState].packet_fn)
arp_states[arpState].packet_fn(cs);
arpreply_clear();
}
// Perform retransmission if necessary.
void handle_arp_timeout(struct client_state_t *cs)
{
if (arp_states[arpState].timeout_fn)
arp_states[arpState].timeout_fn(cs);
}

4
ndhc/arp.h
View File

@@ -1,5 +1,5 @@
/* arp.h - functions to call the interface change daemon
* Time-stamp: <2011-07-06 11:39:42 njk>
* Time-stamp: <2011-07-09 15:39:46 njk>
*
* Copyright 2010-2011 Nicholas J. Kain <njkain@gmail.com>
*
@@ -53,7 +53,7 @@ int arp_check(struct client_state_t *cs, struct dhcpmsg *packet);
int arp_gw_check(struct client_state_t *cs);
void arp_set_defense_mode(struct client_state_t *cs);
void arp_success(struct client_state_t *cs);
void arp_retransmit(struct client_state_t *cs);
void handle_arp_response(struct client_state_t *cs);
void handle_arp_timeout(struct client_state_t *cs);
#endif /* ARP_H_ */

23
ndhc/state.c
View File

@@ -22,8 +22,6 @@ static void bound_timeout(struct client_state_t *cs);
static void renewing_timeout(struct client_state_t *cs);
static void rebinding_timeout(struct client_state_t *cs);
static void released_timeout(struct client_state_t *cs);
static void collision_check_timeout(struct client_state_t *cs);
static void bound_gw_check_timeout(struct client_state_t *cs);
static void xmit_release(struct client_state_t *cs);
static void print_release(struct client_state_t *cs);
static void frenew(struct client_state_t *cs);
@@ -36,14 +34,14 @@ typedef struct {
void (*force_release_fn)(struct client_state_t *cs);
} dhcp_state_t;
dhcp_state_t dhcp_states[] = {
static const dhcp_state_t dhcp_states[] = {
{ selecting_packet, selecting_timeout, 0, print_release}, // SELECTING
{ an_packet, requesting_timeout, 0, print_release}, // REQUESTING
{ 0, bound_timeout, frenew, xmit_release}, // BOUND
{ an_packet, renewing_timeout, 0, xmit_release}, // RENEWING
{ an_packet, rebinding_timeout, 0, xmit_release}, // REBINDING
{ 0, bound_gw_check_timeout, 0, xmit_release}, // BOUND_GW_CHECK
{ 0, collision_check_timeout, 0, xmit_release}, // COLLISION_CHECK
{ 0, 0, 0, xmit_release}, // BOUND_GW_CHECK
{ 0, 0, 0, xmit_release}, // COLLISION_CHECK
{ 0, released_timeout, frenew, 0}, // RELEASED
{ 0, 0, 0, 0}, // NUM_STATES
};
@@ -101,8 +99,6 @@ static void requesting_timeout(struct client_state_t *cs)
// total time, and it is time to renew the lease so that it is not lost.
static void bound_timeout(struct client_state_t *cs)
{
arp_retransmit(cs);
if (curms() < cs->leaseStartTime + cs->renewTime * 1000)
return;
cs->dhcpState = DS_RENEWING;
@@ -139,7 +135,7 @@ static void renewing_timeout(struct client_state_t *cs)
long long elt = cs->leaseStartTime + cs->lease * 1000;
if (ct < elt) {
cs->dhcpState = DS_REBINDING;
cs->timeout = elt - ct / 2;
cs->timeout = (elt - ct) / 2;
log_line("Entering rebinding state.");
} else
lease_timedout(cs);
@@ -169,16 +165,6 @@ static void released_timeout(struct client_state_t *cs)
cs->timeout = -1;
}
static void collision_check_timeout(struct client_state_t *cs)
{
arp_retransmit(cs);
}
static void bound_gw_check_timeout(struct client_state_t *cs)
{
arp_retransmit(cs);
}
// Can transition to DS_BOUND or DS_SELECTING.
static void an_packet(struct client_state_t *cs, struct dhcpmsg *packet,
uint8_t *message)
@@ -332,6 +318,7 @@ void packet_action(struct client_state_t *cs, struct dhcpmsg *packet,
void timeout_action(struct client_state_t *cs)
{
handle_arp_timeout(cs);
if (dhcp_states[cs->dhcpState].timeout_fn)
dhcp_states[cs->dhcpState].timeout_fn(cs);
}