Re: [libvirt] [PATCH 06/10] network: Bridge - Add support for a DHCP Relay Agent

From: TJ <linux(a)iam.tj&gt; A DHCP relay daemon will be started that will forward all DHCP/BOOTP requests on the bridge network via the first declared forward interface.

The relay is broadcast rather than routed so no IP address is needed on the bridge. The XML <relay> element's "relay" property of the active DHCP stanza defaults to 'no'. Set it to 'yes' to enable the relay: <ip ...> <dhcp relay='yes'/> </ip> The relay will not be started if the "enable" property is 'no': <ip ...> <dhcp enable='no' relay='yes'/>

</ip> Signed-off-by: TJ <linux(a)iam.tj&gt; --- src/network/bridge_driver.c | 146 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 146 insertions(+) diff --git a/src/network/bridge_driver.c b/src/network/bridge_driver.c index 8410c93..c02d3de 100644 --- a/src/network/bridge_driver.c +++ b/src/network/bridge_driver.c @@ -587,6 +587,145 @@ cleanup: * which is later saved into a file */ +static virNetworkIpDefPtr +networkGetActiveDhcp(virNetworkObjPtr network) +{ + virNetworkIpDefPtr dhcp = NULL; + + if (network->def && network->def->ipv4_dhcp) + dhcp = network->def->ipv4_dhcp; + + if (!dhcp && + network->def && network->def->ipv6_dhcp) + dhcp = network->def->ipv6_dhcp; + + return dhcp; +} + +static int +networkBuildDhcpRelayArgv(virNetworkObjPtr network, + const char *pidfile, + virCommandPtr cmd) +{ + int ret = -1; + + /* PID file */ + virCommandAddArgList(cmd, "-r", pidfile, NULL); + + /* Listen for DHCP requests on the bridge interface */ + virCommandAddArgList(cmd, "-i", network->def->bridge, NULL); + + /* Use the first forwarding device to broadcast to the upstream DHCP server */ + if (network->def->forward.nifs > 0) { + virCommandAddArgList(cmd, "-b", network->def->forward.ifs[0].device.dev, NULL); + ret = 0; + } else + virReportSystemError(VIR_ERR_INVALID_INTERFACE, + _("DHCP relay requires at least one network %s\n"), + "<forward ... dev='eth?'/> or <interface dev='eth?'/>"); + + return ret; +} + +static int +networkBuildDhcpRelayCommandLine(virNetworkObjPtr network, virCommandPtr *cmdout, + char *pidfile) +{ + virCommandPtr cmd = NULL; + int ret = -1; + + cmd = virCommandNew(DHCPRELAY); + if (networkBuildDhcpRelayArgv(network, pidfile, cmd) < 0) { + goto cleanup; + } + + if (cmdout) + *cmdout = cmd; + ret = 0; +cleanup: + if (ret < 0) + virCommandFree(cmd); + return ret; +} + +static int +networkStartDhcpRelayDaemon(struct network_driver *driver ATTRIBUTE_UNUSED, + virNetworkObjPtr network) +{ + virCommandPtr cmd = NULL; + virNetworkIpDefPtr ipdef = NULL; + char *pidfile = NULL; + char *tmp = NULL; + int pid_len; + int ret = 0; + const char *dhcprelay = "dhcprelay_"; + + ipdef = networkGetActiveDhcp(network); + /* Prepare for DHCP relay agent */ + if (ipdef && ipdef->dhcp_enabled && ipdef->dhcp_relay) { + ret = -1; + + if (virFileMakePath(NETWORK_PID_DIR) < 0) { + virReportSystemError(errno, + _("cannot create directory %s"), + NETWORK_PID_DIR); + goto cleanup; + } + + pid_len = strlen(dhcprelay) + strlen(network->def->name); + if ( VIR_ALLOC_N(tmp, pid_len+1) >= 0) { + tmp = strcpy(tmp, dhcprelay); + tmp = strncat(tmp, network->def->name, pid_len); + if (!(pidfile = virPidFileBuildPath(NETWORK_PID_DIR, tmp))) { + virReportOOMError(); + goto cleanup; + } + } else { + virReportOOMError(); + goto cleanup; + } + + ret = networkBuildDhcpRelayCommandLine(network, &cmd, pidfile); + if (ret < 0) + goto cleanup; + + ret = virCommandRun(cmd, NULL); + if (ret < 0) + goto cleanup; + + ret = virPidFileRead(NETWORK_PID_DIR, pidfile, &network->dhcprelayPid); + if (ret < 0) + virReportSystemError(errno, _("%s is not running"), DHCPRELAY); + +cleanup: + VIR_FREE(tmp); + VIR_FREE(pidfile); + virCommandFree(cmd); + } + return ret; +} + +static int +networkRestartDhcpRelayDaemon(struct network_driver *driver, + virNetworkObjPtr network) +{ + /* if there is a running DHCP relay agent, kill it */ + if (network->dhcprelayPid > 0) { + networkKillDaemon(network->dhcprelayPid, DHCPRELAY, + network->def->name); + network->dhcprelayPid = -1; + } + /* now start the daemon if it should be started */ + return networkStartDhcpRelayDaemon(driver, network); +} + +static int +networkRefreshDhcpRelayDaemon(struct network_driver *driver, + virNetworkObjPtr network) +{ + return networkRestartDhcpRelayDaemon(driver, network); +} + static int networkBuildDnsmasqDhcpHostsList(dnsmasqContext *dctx, virNetworkIpDefPtr ipdef) @@ -1496,6 +1635,7 @@ networkRefreshDaemons(struct network_driver *driver) * dnsmasq and/or radvd, or restart them if they've * disappeared. */ + networkRefreshDhcpRelayDaemon(driver, network); networkRefreshDhcpDaemon(driver, network); networkRefreshRadvd(driver, network); } @@ -2462,6 +2602,10 @@ networkStartNetworkVirtual(struct network_driver *driver, networkStartDhcpDaemon(driver, network) < 0) goto err3; + /* start DHCP relay-agent (doesn't need IP address(es) to function) */ + if (networkStartDhcpRelayDaemon(driver, network) < 0) + goto err3; + /* start radvd if there are any ipv6 addresses */ if (v6present && networkStartRadvd(driver, network) < 0) goto err4; @@ -3276,6 +3420,8 @@ networkUpdate(virNetworkPtr net, */ if (networkRestartDhcpDaemon(driver, network) < 0) goto cleanup; + if (networkRestartDhcpRelayDaemon(driver, network) < 0) + goto cleanup; } else if (section == VIR_NETWORK_SECTION_IP_DHCP_HOST) { /* if we previously weren't listening for dhcp and now we