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sd-dhcp-client: correct dhcpv4 renew/rebind retransmit timeouts 

Use the request timeout algorithm specified in RFC2131 section 4.4.5 for
handling timed out RENEW and REBIND requests.

This changes behavior, as previously only 2 RENEW and 2 REBIND requests
were sent, no matter how long the lease lifetime. Now, requests are
send according to the RFC, which results in starting with a timeout
of 1/2 the t1 or t2 period, and halving the timeout for each retry
down to a minimum of 60 seconds.

Fixes: #17909
This commit is contained in:
Dan Streetman 2020-12-08 15:40:10 -05:00
parent b0d7d8063c
commit c24288d21e
1 changed files with 3 additions and 13 deletions
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16
src/libsystemd-network/sd-dhcp-client.c
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@ -1227,7 +1227,6 @@ static int client_timeout_resend(
DHCP_CLIENT_DONT_DESTROY(client);
usec_t next_timeout;
uint64_t time_now;
uint32_t time_left;
int r;
assert(s);
@ -1241,19 +1240,11 @@ static int client_timeout_resend(
switch (client->state) {
case DHCP_STATE_RENEWING:
time_left = (client->lease->t2 - client->lease->t1) / 2;
if (time_left < 60)
time_left = 60;
next_timeout = time_now + time_left * USEC_PER_SEC;
next_timeout = client_compute_reacquisition_timeout(time_now, client->t2_time);
break;
case DHCP_STATE_REBINDING:
time_left = (client->lease->lifetime - client->lease->t2) / 2;
if (time_left < 60)
time_left = 60;
next_timeout = time_now + time_left * USEC_PER_SEC;
next_timeout = client_compute_reacquisition_timeout(time_now, client->expire_time);
break;
case DHCP_STATE_REBOOTING:
@ -1279,6 +1270,7 @@ static int client_timeout_resend(
client->attempt++;
next_timeout = time_now + ((UINT64_C(1) << MIN(client->attempt, (uint64_t) 6)) - 1) * USEC_PER_SEC;
next_timeout += (random_u32() & 0x1fffff);
break;
case DHCP_STATE_STOPPED:
@ -1286,8 +1278,6 @@ static int client_timeout_resend(
goto error;
}
next_timeout += (random_u32() & 0x1fffff);
r = event_reset_time(client->event, &client->timeout_resend,
clock_boottime_or_monotonic(),
next_timeout, 10 * USEC_PER_MSEC,