[libvirt] [PATCH 3/3] network driver: Use a separate dhcp leases file for each network

By default, all dnsmasq processes share the same leases file. libvirt also uses the --dhcp-lease-max option to control the maximum number of leases allowed. The problem is that libvirt puts in a number equal to the number of addresses in the range for the one network handled by a single instance of dnsmasq, but dnsmasq checks the total number of leases in the file (which could potentially contain many more). The solution is to tell each instance of dnsmasq to create and use its own leases file. (/var/lib/libvirt/network/<net-name>.leases). This file is created by dnsmasq when it starts, but not deleted when it exists. This is fine when the network is just being stopped, but if the leases file was left around when a network was undefined, we could end up with an ever-increasing number of dead files - instead, we explicitly unlink the leases file when a network is undefined. Note that Ubuntu carries a patch against an older version of libvirt for this: hhttps://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/713071 ttp://bazaar.launchpad.net/~serge-hallyn/ubuntu/maverick/libvirt/bugall/r... I was certain I'd also seen discussion of this on libvir-list or libvirt-users, but couldn't find it. --- src/network/bridge_driver.c | 22 ++++++++++++++++++++++ 1 files changed, 22 insertions(+), 0 deletions(-) diff --git a/src/network/bridge_driver.c b/src/network/bridge_driver.c index 484f35e..1fd179c 100644 --- a/src/network/bridge_driver.c +++ b/src/network/bridge_driver.c @@ -109,6 +109,16 @@ static void networkReloadIptablesRules(struct network_driver *driver); static struct network_driver *driverState = NULL; static char * +networkDnsmasqLeaseFileName(const char *netname) +{ + char *leasefile; + + virAsprintf(&leasefile, DNSMASQ_STATE_DIR "/%s.leases", + netname); + return leasefile; +} + +static char * networkRadvdPidfileBasename(const char *netname) { /* this is simple but we want to be sure it's consistently done */ @@ -531,6 +541,11 @@ networkBuildDnsmasqArgv(virNetworkObjPtr network, } if (ipdef->nranges > 0) { + char *leasefile = networkDnsmasqLeaseFileName(network->def->name); + if (!leasefile) + goto cleanup; + virCommandAddArgFormat(cmd, "--dhcp-leasefile=%s", leasefile); + VIR_FREE(leasefile); virCommandAddArgFormat(cmd, "--dhcp-lease-max=%d", nbleases); } @@ -2195,12 +2210,19 @@ static int networkUndefine(virNetworkPtr net) { } if (dhcp_present) { + char *leasefile; dnsmasqContext *dctx = dnsmasqContextNew(network->def->name, DNSMASQ_STATE_DIR); if (dctx == NULL) goto cleanup; dnsmasqDelete(dctx); dnsmasqContextFree(dctx); + + leasefile = networkDnsmasqLeaseFileName(network->def->name); + if (!leasefile) + goto cleanup; + unlink(leasefile); + VIR_FREE(leasefile); } if (v6present) { -- 1.7.3.4