We already check that any auto-assigned bridge device name for a virtual network (e.g. "virbr1") doesn't conflict with the bridge name for any existing libvirt network (via virNetworkSetBridgeName() in conf/network_conf.c). We also want to check that the name doesn't conflict with any bridge device created on the host system outside the control of libvirt (history: possibly due to the ploriferation of references to libvirt's bridge devices in HOWTO documents all around the web, it is not uncommon for an admin to manually create a bridge in their host's system network config and name it "virbrX"). To add such a check to virNetworkBridgeInUse() (which is called by virNetworkSetBridgeName()) we would have to call virNetDevExists() (from util/virnetdev.c); this function calls ioctl(SIOCGIFFLAGS), which everyone on the mailing list agreed should not be done from an XML parsing function in the conf directory. To remedy that problem, this patch removes virNetworkSetBridgeName() from conf/network_conf.c and puts an identically functioning networkBridgeNameValidate() in network/bridge_driver.c (because it's reasonable for the bridge driver to call virNetDevExists(), although we don't do that yet because I wanted this patch to have as close to 0 effect on function as possible). There are a couple of inevitable changes though: 1) We no longer check the bridge name during virNetworkLoadConfig(). Close examination of the code shows that this wasn't necessary anyway - the only *correct* way to get XML into the config files is via networkDefine(), and networkDefine() will always call networkValidate(), which previously called virNetworkSetBridgeName() (and now calls networkBridgeNameValidate()). This means that the only way the bridge name can be unset during virNetworkLoadConfig() is if someone edited the config file on disk by hand (which we explicitly prohibit). 2) Just on the off chance that somebody *has* edited the file by hand, rather than crashing when they try to start their malformed network, a check for non-NULL bridge name has been added to networkStartNetworkVirtual(). (For those wondering why I don't instead call networkValidateBridgeName() there to set a bridge name if one wasn't present - the problem is that during networkStartNetworkVirtual(), the lock for the network being started has already been acquired, but the lock for the network list itself *has not* (because we aren't adding/removing a network). But virNetworkBridgeInuse() iterates through *all* networks (including this one) and locks each network as it is checked for a duplicate entry; it is necessary to lock each network even before checking if it is the designated "skip" network because otherwise some other thread might acquire the list lock and delete the very entry we're examining. In the end, permitting a setting of the bridge name during network start would require that we lock the entire network list during any networkStartNetwork(), which eliminates a *lot* of parallelism that we've worked so hard to achieve (it can make a huge difference during libvirtd startup). So rather than try to adjust for someone playing against the rules, I choose to instead give them the error they deserve.) 3) virNetworkAllocateBridge() (now removed) would leak any "template" string set as the bridge name. Its replacement networkFindUnusedBridgeName() doesn't leak the template string - it is properly freed. --- src/conf/network_conf.c | 60 ------------------------------ src/conf/network_conf.h | 9 +---- src/libvirt_private.syms | 2 +- src/network/bridge_driver.c | 89 ++++++++++++++++++++++++++++++++++++++++++++- 4 files changed, 90 insertions(+), 70 deletions(-) diff --git a/src/conf/network_conf.c b/src/conf/network_conf.c index f4a9df0..aa8d6c6 100644 --- a/src/conf/network_conf.c +++ b/src/conf/network_conf.c @@ -45,7 +45,6 @@ #include "virfile.h" #include "virstring.h" -#define MAX_BRIDGE_ID 256 #define VIR_FROM_THIS VIR_FROM_NETWORK /* currently, /sbin/tc implementation allows up to 16 bits for minor class size */ #define CLASS_ID_BITMAP_SIZE (1<<16) @@ -3123,11 +3122,6 @@ virNetworkObjPtr virNetworkLoadConfig(virNetworkObjListPtr nets, virNetworkSetBridgeMacAddr(def); virNetworkSaveConfig(configDir, def); } - /* Generate a bridge if none is specified, but don't check for collisions - * if a bridge is hardcoded, so the network is at least defined. - */ - if (virNetworkSetBridgeName(nets, def, 0)) - goto error; } else { /* Throw away MAC address for other forward types, * which could have been generated by older libvirt RPMs */ @@ -3303,60 +3297,6 @@ int virNetworkBridgeInUse(virNetworkObjListPtr nets, return obj != NULL; } -char *virNetworkAllocateBridge(virNetworkObjListPtr nets, - const char *template) -{ - - int id = 0; - char *newname; - - if (!template) - template = "virbr%d"; - - do { - if (virAsprintf(&newname, template, id) < 0) - return NULL; - if (!virNetworkBridgeInUse(nets, newname, NULL)) - return newname; - VIR_FREE(newname); - - id++; - } while (id <= MAX_BRIDGE_ID); - - virReportError(VIR_ERR_INTERNAL_ERROR, - _("Bridge generation exceeded max id %d"), - MAX_BRIDGE_ID); - return NULL; -} - -int virNetworkSetBridgeName(virNetworkObjListPtr nets, - virNetworkDefPtr def, - int check_collision) -{ - int ret = -1; - - if (def->bridge && !strstr(def->bridge, "%d")) { - /* We may want to skip collision detection in this case (ex. when - * loading configs at daemon startup, so the network is at least - * defined. */ - if (check_collision && - virNetworkBridgeInUse(nets, def->bridge, def->name)) { - virReportError(VIR_ERR_INTERNAL_ERROR, - _("bridge name '%s' already in use."), - def->bridge); - goto error; - } - } else { - /* Allocate a bridge name */ - if (!(def->bridge = virNetworkAllocateBridge(nets, def->bridge))) - goto error; - } - - ret = 0; - error: - return ret; -} - void virNetworkSetBridgeMacAddr(virNetworkDefPtr def) { diff --git a/src/conf/network_conf.h b/src/conf/network_conf.h index f69d999..9411a02 100644 --- a/src/conf/network_conf.h +++ b/src/conf/network_conf.h @@ -1,7 +1,7 @@ /* * network_conf.h: network XML handling * - * Copyright (C) 2006-2014 Red Hat, Inc. + * Copyright (C) 2006-2015 Red Hat, Inc. * Copyright (C) 2006-2008 Daniel P. Berrange * * This library is free software; you can redistribute it and/or @@ -401,13 +401,6 @@ int virNetworkBridgeInUse(virNetworkObjListPtr nets, const char *bridge, const char *skipname); -char *virNetworkAllocateBridge(virNetworkObjListPtr nets, - const char *template); - -int virNetworkSetBridgeName(virNetworkObjListPtr nets, - virNetworkDefPtr def, - int check_collision); - void virNetworkSetBridgeMacAddr(virNetworkDefPtr def); int diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms index 8c50ea2..ae318dc 100644 --- a/src/libvirt_private.syms +++ b/src/libvirt_private.syms @@ -570,6 +570,7 @@ virNetDevVPortTypeToString; # conf/network_conf.h virNetworkAssignDef; +virNetworkBridgeInUse; virNetworkBridgeMACTableManagerTypeFromString; virNetworkBridgeMACTableManagerTypeToString; virNetworkConfigChangeSetup; @@ -612,7 +613,6 @@ virNetworkRemoveInactive; virNetworkSaveConfig; virNetworkSaveStatus; virNetworkSetBridgeMacAddr; -virNetworkSetBridgeName; virNetworkTaintTypeFromString; virNetworkTaintTypeToString; virPortGroupFindByName; diff --git a/src/network/bridge_driver.c b/src/network/bridge_driver.c index d195085..abacae3 100644 --- a/src/network/bridge_driver.c +++ b/src/network/bridge_driver.c @@ -76,6 +76,7 @@ #include "virjson.h" #define VIR_FROM_THIS VIR_FROM_NETWORK +#define MAX_BRIDGE_ID 256 /** * VIR_NETWORK_DHCP_LEASE_FILE_SIZE_MAX: @@ -449,6 +450,7 @@ networkUpdateState(virNetworkObjPtr obj, return ret; } + static int networkAutostartConfig(virNetworkObjPtr net, void *opaque) @@ -2034,6 +2036,18 @@ networkStartNetworkVirtual(virNetworkDriverStatePtr driver, return -1; /* Create and configure the bridge device */ + if (!network->def->bridge) { + /* this can only happen if the config files were edited + * directly. Otherwise networkValidate() (called after parsing + * the XML from networkCreateXML() and networkDefine()) + * guarantees we will have a valid bridge name before this + * point. + */ + virReportError(VIR_ERR_INTERNAL_ERROR, + _("network '%s' has no bridge name defined"), + network->def->name); + return -1; + } if (virNetDevBridgeCreate(network->def->bridge) < 0) return -1; @@ -2746,6 +2760,76 @@ static int networkIsPersistent(virNetworkPtr net) } +/* + * networkFindUnusedBridgeName() - try to find a bridge name that is + * unused by the currently configured libvirt networks, and set this + * network's name to that new name. + */ +static int +networkFindUnusedBridgeName(virNetworkObjListPtr nets, + virNetworkDefPtr def) +{ + + int ret = -1, id = 0; + char *newname = NULL; + const char *templ = def->bridge ? def->bridge : "virbr%d"; + + do { + if (virAsprintf(&newname, templ, id) < 0) + goto cleanup; + if (!virNetworkBridgeInUse(nets, newname, def->name)) { + VIR_FREE(def->bridge); /*could contain template */ + def->bridge = newname; + ret = 0; + goto cleanup; + } + VIR_FREE(newname); + } while (++id <= MAX_BRIDGE_ID); + + virReportError(VIR_ERR_INTERNAL_ERROR, + _("Bridge generation exceeded max id %d"), + MAX_BRIDGE_ID); + ret = 0; + cleanup: + if (ret < 0) + VIR_FREE(newname); + return ret; +} + + + +/* + * networkValidateBridgeName() - if no bridge name is set, or if the + * bridge name contains a %d (indicating that this is a template for + * the actual name) try to set an appropriate bridge name. If a + * bridge name *is* set, make sure it doesn't conflict with any other + * network's bridge name. + */ +static int +networkBridgeNameValidate(virNetworkObjListPtr nets, + virNetworkDefPtr def) +{ + int ret = -1; + + if (def->bridge && !strstr(def->bridge, "%d")) { + if (virNetworkBridgeInUse(nets, def->bridge, def->name)) { + virReportError(VIR_ERR_INTERNAL_ERROR, + _("bridge name '%s' already in use."), + def->bridge); + goto cleanup; + } + } else { + /* Allocate a bridge name */ + if (networkFindUnusedBridgeName(nets, def) < 0) + goto cleanup; + } + + ret = 0; + cleanup: + return ret; +} + + static int networkValidate(virNetworkDriverStatePtr driver, virNetworkDefPtr def) @@ -2765,7 +2849,10 @@ networkValidate(virNetworkDriverStatePtr driver, def->forward.type == VIR_NETWORK_FORWARD_NAT || def->forward.type == VIR_NETWORK_FORWARD_ROUTE) { - if (virNetworkSetBridgeName(driver->networks, def, 1)) + /* if no bridge name was given in the config, find a name + * unused by any other libvirt networks and assign it. + */ + if (networkBridgeNameValidate(driver->networks, def) < 0) return -1; virNetworkSetBridgeMacAddr(def); -- 2.1.0

Thanks for the patches Laine. I agree pretty much with both the patches. also had a chance to try these out. Only scenario I see a trouble is, net-create without bridge name in the xml, followed by net-define using the same xml file. The live and --inactive xmls both show different bridge names, though the active bridge can be reused by the network for "this scenario alone". I think this is a very rare case and not worth to fix it, as net-destroy followed by net-create using the same xml file would anyway reuse the same old bridge name if available. Outside of this patch, the net->newDef->bridge's are not considered in virNetworkBridgeInUseHelper(). Do we need to? Thanks, Shiva On Fri, Apr 24, 2015 at 12:33 AM, Laine Stump <laine(a)laine.org&gt; wrote:

On Sat, Apr 25, 2015 at 12:11 AM, Laine Stump <laine(a)laine.org&gt; wrote: Certainly! ACK the first two patches. The third patch, I am leaving a comment there. Thanks, Shiva

On Sat, Apr 25, 2015 at 12:14 AM, Laine Stump <laine(a)laine.org&gt; wrote: Should the newDef->name be really be checked? The network cant be renamed. Right ? Thanks, Shiva

On Mon, Apr 27, 2015 at 11:20 PM, Laine Stump <laine(a)laine.org&gt; wrote: Thanks for the explanation Laine. Given possible future plans, I agree it makes sense to have this check for now. ACK