This fixes a regression introduced in commit ad48df, and reported on the libvirt-users list: https://www.redhat.com/archives/libvirt-users/2011-March/msg00018.html The problem in that commit was that we began searching a list of ip address definitions (rather than just having one) to look for a dhcp range or static host; when we didn't find any, our pointer (ipdef) was left at NULL, and when ipdef was NULL, we returned without starting up dnsmasq. Previously dnsmasq was started even without any dhcp ranges or static entries, because it's still useful for DNS services. Another problem I noticed while investigating was that, if there are IPv6 addresses, but no IPv4 addresses of any kind, we would jump out at an ever higher level in the call chain. This patch does the following: 1) networkBuildDnsmasqArgv() = all uses of ipdef are protected from NULL dereference. (this patch doesn't change indentation, to make review easier. The next patch will change just the indentation). ipdef is intended to point to the first IPv4 address with DHCP info (or the first IPv4 address if none of them have any dhcp info). 2) networkStartDhcpDaemon() = if the loop looking for an ipdef with DHCP info comes up empty, we then grab the first IPv4 def from the list. Also, instead of returning if there are no IPv4 defs, we just return if there are no IP defs at all (either v4 or v6). This way a network that is IPv6-only will still get dnsmasq listening for DNS queries. 3) in networkStartNetworkDaemon() - we will startup dhcp not just if there are any IPv4 addresses, but also if there are any IPv6 addresses. --- src/network/bridge_driver.c | 21 ++++++++++++++++----- 1 files changed, 16 insertions(+), 5 deletions(-) diff --git a/src/network/bridge_driver.c b/src/network/bridge_driver.c index e666cbb..e3156fa 100644 --- a/src/network/bridge_driver.c +++ b/src/network/bridge_driver.c @@ -440,12 +440,9 @@ networkBuildDnsmasqArgv(virNetworkObjPtr network, virCommandPtr cmd) { int r, ret = -1; int nbleases = 0; - char *bridgeaddr; int ii; virNetworkIpDefPtr tmpipdef; - if (!(bridgeaddr = virSocketFormatAddr(&ipdef->address))) - goto cleanup; /* * NB, be careful about syntax for dnsmasq options in long format. * @@ -501,6 +498,7 @@ networkBuildDnsmasqArgv(virNetworkObjPtr network, VIR_FREE(ipaddr); } + if (ipdef) { for (r = 0 ; r < ipdef->nranges ; r++) { char *saddr = virSocketFormatAddr(&ipdef->ranges[r].start); if (!saddr) @@ -524,8 +522,12 @@ networkBuildDnsmasqArgv(virNetworkObjPtr network, * dnsmasq. */ if (!ipdef->nranges && ipdef->nhosts) { + char *bridgeaddr = virSocketFormatAddr(&ipdef->address); + if (!bridgeaddr) + goto cleanup; virCommandAddArg(cmd, "--dhcp-range"); virCommandAddArgFormat(cmd, "%s,static", bridgeaddr); + VIR_FREE(bridgeaddr); } if (ipdef->nranges > 0) { @@ -569,10 +571,10 @@ networkBuildDnsmasqArgv(virNetworkObjPtr network, virCommandAddArg(cmd, ipdef->bootfile); } } + } ret = 0; cleanup: - VIR_FREE(bridgeaddr); return ret; } @@ -594,7 +596,16 @@ networkStartDhcpDaemon(virNetworkObjPtr network) if (ipdef->nranges || ipdef->nhosts) break; } + /* If no IPv4 addresses had dhcp info, pick the first (if there were any). */ if (!ipdef) + ipdef = virNetworkDefGetIpByIndex(network->def, AF_INET, 0); + + /* If there are no IP addresses at all (v4 or v6), return now, since + * there won't be any address for dnsmasq to listen on anyway. + * If there are any addresses, even if no dhcp ranges or static entries, + * we should continue and run dnsmasq, just for the DNS capabilities. + */ + if (!virNetworkDefGetIpByIndex(network->def, AF_UNSPEC, 0)) return 0; if ((err = virFileMakePath(NETWORK_PID_DIR)) != 0) { @@ -1678,7 +1689,7 @@ networkStartNetworkDaemon(struct network_driver *driver, /* start dnsmasq if there are any IPv4 addresses */ - if (v4present && networkStartDhcpDaemon(network) < 0) + if ((v4present || v6present) && networkStartDhcpDaemon(network) < 0) goto err3; /* start radvd if there are any ipv6 addresses */ -- 1.7.3.4

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/revision/109 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