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dhcp/nettools: exactly calculate lease lifetimes

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Now that we can not only get the expiry timestamp of the lease
(n_dhcp4_client_lease_get_lifetime()), but also the base timestamp,
we can calculate the lifetime exactly.

Previously, we had to guess the base time by assuming that we just
received the lease *now*. This wasn't exact.
This commit is contained in:
Thomas Haller
2019-11-20 11:19:06 +01:00
parent a8d46492b3
commit 0108d74866
1 changed files with 41 additions and 21 deletions
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62
src/dhcp/nm-dhcp-nettools.c
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@@ -348,15 +348,14 @@ lease_parse_address (NDhcp4ClientLease *lease,
GError **error)
{
char addr_str[NM_UTILS_INET_ADDRSTRLEN];
const gint64 ts = nm_utils_get_monotonic_timestamp_ns ();
const gint64 ts_clock_boottime = nm_utils_monotonic_timestamp_as_boottime (ts, 1);
struct in_addr a_address;
struct in_addr a_netmask;
struct in_addr a_next_server;
guint32 a_plen;
guint64 nettools_lifetime;
gint64 a_lifetime;
gint64 a_expiry;
guint32 a_lifetime;
guint32 a_timestamp;
guint64 a_expiry;
n_dhcp4_client_lease_get_yiaddr (lease, &a_address);
if (a_address.s_addr == INADDR_ANY) {
@@ -364,26 +363,47 @@ lease_parse_address (NDhcp4ClientLease *lease,
return FALSE;
}
/* n_dhcp4_client_lease_get_lifetime() never fails */
n_dhcp4_client_lease_get_lifetime (lease, &nettools_lifetime);
/* FIXME: n_dhcp4_client_lease_get_lifetime() returns the time in nsec of CLOCK_BOOTTIME.
* We want to retrieve the original lifetime value in seconds, so we approximate it in a_lifetime.
* Use a nettools API to retrieve the original value as passed by the server.
*/
if (nettools_lifetime == G_MAXUINT64) {
a_timestamp = 0;
a_lifetime = NM_PLATFORM_LIFETIME_PERMANENT;
a_expiry = -1;
a_expiry = G_MAXUINT64;
} else {
gint64 ts_time = time (NULL);
guint64 nettools_basetime;
guint64 lifetime;
gint64 ts;
a_lifetime = ((gint64) nettools_lifetime - ts_clock_boottime + (NM_UTILS_NS_PER_SECOND / 2)) / NM_UTILS_NS_PER_SECOND;
/* A lease time of 0 is allowed on some dhcp servers, so, let's accept it. */
if (a_lifetime < 0)
a_lifetime = 0;
else if (a_lifetime > NM_PLATFORM_LIFETIME_PERMANENT)
a_lifetime = NM_PLATFORM_LIFETIME_PERMANENT - 1;
n_dhcp4_client_lease_get_basetime (lease, &nettools_basetime);
a_expiry = ts_time + a_lifetime;
/* usually we shouldn't assert against external libraries like n-dhcp4.
* Here we still do it... it seems safe enough. */
nm_assert (nettools_basetime > 0);
nm_assert (nettools_lifetime >= nettools_basetime);
nm_assert (((nettools_lifetime - nettools_basetime) % NM_UTILS_NS_PER_SECOND) == 0);
nm_assert ((nettools_lifetime - nettools_basetime) <= G_MAXUINT32);
if (nettools_lifetime <= nettools_basetime) {
/* A lease time of 0 is allowed on some dhcp servers, so, let's accept it. */
lifetime = 0;
} else {
lifetime = nettools_lifetime - nettools_basetime;
/* we "ceil" the value to the next second. In practice, we don't expect any sub-second values
* from n-dhcp4 anyway, so this should have no effect. */
lifetime += NM_UTILS_NS_PER_SECOND - 1;
}
ts = nm_utils_monotonic_timestamp_from_boottime (nettools_basetime, 1);
/* the timestamp must be positive, because we only started nettools DHCP client
* after obtaining the first monotonic timestamp. Hence, the lease must have been
* received afterwards. */
nm_assert (ts >= NM_UTILS_NS_PER_SECOND);
a_timestamp = ts / NM_UTILS_NS_PER_SECOND;
a_lifetime = NM_MIN (lifetime / NM_UTILS_NS_PER_SECOND, NM_PLATFORM_LIFETIME_PERMANENT - 1);
a_expiry = time (NULL) + ((lifetime - (nm_utils_clock_gettime_ns (CLOCK_BOOTTIME) - nettools_basetime)) / NM_UTILS_NS_PER_SECOND);
}
if (!lease_get_in_addr (lease, NM_DHCP_OPTION_DHCP4_SUBNET_MASK, &a_netmask)) {
@@ -408,11 +428,11 @@ lease_parse_address (NDhcp4ClientLease *lease,
NM_DHCP_OPTION_DHCP4_IP_ADDRESS_LEASE_TIME,
(guint64) a_lifetime);
if (a_expiry != -1) {
if (a_expiry != G_MAXUINT64) {
nm_dhcp_option_add_option_u64 (options,
_nm_dhcp_option_dhcp4_options,
NM_DHCP_OPTION_DHCP4_NM_EXPIRY,
(guint64) a_expiry);
a_expiry);
}
@@ -431,7 +451,7 @@ lease_parse_address (NDhcp4ClientLease *lease,
.peer_address = a_address.s_addr,
.plen = a_plen,
.addr_source = NM_IP_CONFIG_SOURCE_DHCP,
.timestamp = ts / NM_UTILS_NS_PER_SECOND,
.timestamp = a_timestamp,
.lifetime = a_lifetime,
.preferred = a_lifetime,
}));