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Make renew and rebinding directly track whether DHCPREQUEST was sent.
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Before it was inferred by examining timeouts.  Also, simplify
the associated timeout code so that there are no longer effectively
two redundant paths.
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@niklata
niklata committed Oct 19, 2020
1 parent 4df035c commit f436589
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Showing 2 changed files with 16 additions and 36 deletions.
3 changes: 2 additions & 1 deletion src/ndhc.h
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Original file line number Diff line number Diff line change
Expand Up @@ -53,7 +53,8 @@ struct client_state_t {
uint32_t lease, xid;
uint8_t routerArp[6], serverArp[6];
enum arp_state server_arp_state, router_arp_state;
bool using_dhcp_bpf, arp_is_defense, check_fingerprint, program_init;
bool using_dhcp_bpf, arp_is_defense, check_fingerprint, program_init,
sent_renew_or_rebind;
bool sent_gw_query, sent_first_announce, sent_second_announce,
init_fingerprint_inprogress;
};
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49 changes: 14 additions & 35 deletions src/state.c
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Original file line number Diff line number Diff line change
Expand Up @@ -83,6 +83,7 @@ static void reinit_shared_deconfig(struct client_state_t cs[static 1])
cs->server_arp_state = ARP_QUERY;
cs->router_arp_state = ARP_QUERY;
cs->check_fingerprint = false;
cs->sent_renew_or_rebind = false;
cs->sent_gw_query = false;
cs->sent_first_announce = false;
cs->sent_second_announce = false;
Expand Down Expand Up @@ -120,24 +121,10 @@ static int requesting_timeout(struct client_state_t cs[static 1],
return REQ_SUCCESS;
}

static bool is_renewing(struct client_state_t cs[static 1], long long nowts)
{
long long rnt = cs->leaseStartTime + cs->renewTime * 1000;
return nowts >= rnt;
}

static bool is_rebinding(struct client_state_t cs[static 1], long long nowts)
{
long long rbt = cs->leaseStartTime + cs->rebindTime * 1000;
return nowts >= rbt;
}

// Triggered when a DHCP rebind request has been sent and no reply has been
// received within the response wait time. Check to see if the lease is still
// valid, and if it is, send a broadcast DHCP renew packet. If it is not, then
// change to the SELECTING state to get a new lease.
// Called by renewing_timeout() to try to renew the lease. If all
// timeouts expire, then expire the lease and notify the caller.
static int rebinding_timeout(struct client_state_t cs[static 1],
long long nowts)
long long nowts)
{
long long elt = cs->leaseStartTime + cs->lease * 1000;
if (nowts >= elt) {
Expand All @@ -152,19 +139,15 @@ static int rebinding_timeout(struct client_state_t cs[static 1],
client_config.interface);
return BTO_HARDFAIL;
}
cs->sent_renew_or_rebind = true;
long long ts0 = nowts + (50 + nk_random_u32(&cs->rnd_state) % 20) * 1000;
cs->dhcp_wake_ts = ts0 < elt ? ts0 : elt;
return BTO_WAIT;
}

// Triggered when a DHCP renew request has been sent and no reply has been
// received within the response wait time. This function is also directly
// called by bound_timeout() when it is time to renew a lease before it
// expires. Check to see if the lease is still valid, and if it is, send
// a unicast DHCP renew packet. If it is not, then change to the REBINDING
// state to send broadcast queries.
// Called by bound_timeout() to try to renew the lease.
static int renewing_timeout(struct client_state_t cs[static 1],
long long nowts)
long long nowts)
{
long long rbt = cs->leaseStartTime + cs->rebindTime * 1000;
if (nowts >= rbt)
Expand All @@ -175,13 +158,14 @@ static int renewing_timeout(struct client_state_t cs[static 1],
client_config.interface);
return BTO_HARDFAIL;
}
cs->sent_renew_or_rebind = true;
long long ts0 = nowts + (50 + nk_random_u32(&cs->rnd_state) % 20) * 1000;
cs->dhcp_wake_ts = ts0 < rbt ? ts0 : rbt;
return BTO_WAIT;
}

// Triggered when the lease has been held for a significant fraction of its
// total time, and it is time to renew the lease so that it is not lost.
// Called to handle dhcp state timeouts, such as when RENEW or REBIND
// DHCPREQUESTs must be sent. Can return BTO_(WAIT|EXPIRED|HARDFAIL).
static int bound_timeout(struct client_state_t cs[static 1], long long nowts)
{
long long rnt = cs->leaseStartTime + cs->renewTime * 1000;
Expand Down Expand Up @@ -245,6 +229,7 @@ static int extend_packet(struct client_state_t cs[static 1],
if (msgtype == DHCPACK) {
if (!validate_serverid(cs, packet, "a DHCP ACK"))
return ANP_IGNORE;
cs->sent_renew_or_rebind = false;
get_leasetime(cs, packet);

// Did we receive a lease with a different IP than we had before?
Expand All @@ -267,6 +252,7 @@ static int extend_packet(struct client_state_t cs[static 1],
} else if (msgtype == DHCPNAK) {
if (!validate_serverid(cs, packet, "a DHCP NAK"))
return ANP_IGNORE;
cs->sent_renew_or_rebind = false;
log_line("%s: Our request was rejected. Searching for a new lease...",
client_config.interface);
reinit_selecting(cs, 3000);
Expand Down Expand Up @@ -595,7 +581,7 @@ int dhcp_handle(struct client_state_t cs[static 1], long long nowts,
}
}
}
if (sev_dhcp && is_renewing(cs, nowts)) {
if (sev_dhcp && cs->sent_renew_or_rebind) {
int r = extend_packet(cs, dhcp_packet, dhcp_msgtype, dhcp_srcaddr);
if (r == ANP_SUCCESS || r == ANP_IGNORE) {
} else if (r == ANP_REJECTED) {
Expand Down Expand Up @@ -701,14 +687,7 @@ int dhcp_handle(struct client_state_t cs[static 1], long long nowts,
} else BAD_STATE();
}
if (dhcp_timeout) {
int r;
if (is_rebinding(cs, nowts)) {
r = rebinding_timeout(cs, nowts);
} else if (is_renewing(cs, nowts)) {
r = renewing_timeout(cs, nowts);
} else {
r = bound_timeout(cs, nowts);
}
int r = bound_timeout(cs, nowts);
if (r == BTO_WAIT) {
} else if (r == BTO_EXPIRED) {
sev_dhcp = false;
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