[Dnsmasq-discuss] [libvirt] [PATCHv3 1/2] network: added waiting for DAD to finish for bridge address.
Simon Kelley
simon at thekelleys.org.uk
Tue Aug 11 09:14:36 BST 2015
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On 10/08/15 22:29, Laine Stump wrote:
> On 08/10/2015 01:08 PM, Maxim Perevedentsev wrote:
>> This is a fix for commit
>> db488c79173b240459c7754f38c3c6af9b432970 dnsmasq main process
>> exits without waiting for DAD, this is dnsmasq daemon's task. So
>> we periodically poll the kernel using netlink and check whether
>> there are any IPv6 addresses assigned to bridge which have
>> 'tentative' state. After DAD is finished, execution continues. I
>> guess that is what dnsmasq was assumed to do.
>
> Since the comments in our code imply that dnsmasq should be waiting
> for DAD to complete prior to daemonizing, before pushing a fix like
> this I'd like to find out from the dnsmasq folks if we are
> erroneously relying on nonexistent dnsmasq behavior, or if maybe
> there is a bug in some version of dnsmasq.
>
> Simon (or other dnsmasq people) - when dnsmasq is run with
> "enable-ra", does it make sure it completes DAD prior to
> daemonizing? Or does libvirt need to do this extra polling to
> assure that DAD has completed? (or maybe there's some other config
> parameter we need to add?)
>
>
Dnsmasq doesn't wait for DAD to complete before returning. Internally,
it know is DAD is still happening on an interface, as it needs to
delay calling bind() until after it's complete. It would, therefore be
relatively simple to add this behaviour, but it's not a complete
solution, since new interfaces can appear _after_ dnsmasq has
completed start-up.
Having libvirt do its own checks whenever it creates an interface
might therefore be a cleaner way of doing things, but I don't have an
objection to changing dnsmasq behaviour if there's a good reason why
that's not sensible.
Cheers,
Simon.
>
>> --- Difference to v2: Moved to virnetdev.
>>
>> src/libvirt_private.syms | 1 + src/network/bridge_driver.c |
>> 35 +++++++++- src/util/virnetdev.c | 160
>> ++++++++++++++++++++++++++++++++++++++++++++ src/util/virnetdev.h
>> | 2 + 4 files changed, 197 insertions(+), 1 deletion(-)
>>
>> diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
>> index 0517c24..fa9e1c1 100644 --- a/src/libvirt_private.syms +++
>> b/src/libvirt_private.syms @@ -1776,6 +1776,7 @@
>> virNetDevSetRcvMulti; virNetDevSetupControl; virNetDevSysfsFile;
>> virNetDevValidateConfig; +virNetDevWaitDadFinish;
>>
>>
>> # util/virnetdevbandwidth.h diff --git
>> a/src/network/bridge_driver.c b/src/network/bridge_driver.c index
>> 3d6721b..2172a3d 100644 --- a/src/network/bridge_driver.c +++
>> b/src/network/bridge_driver.c @@ -2026,6 +2026,33 @@
>> networkAddRouteToBridge(virNetworkObjPtr network, }
>>
>> static int +networkWaitDadFinish(virNetworkObjPtr network) +{ +
>> virNetworkIpDefPtr ipdef; + virSocketAddrPtr *addrs = NULL; +
>> size_t i; + int ret; + for (i = 0; + (ipdef =
>> virNetworkDefGetIpByIndex(network->def, AF_INET6, i)); +
>> i++) {} + + if (i == 0) + return 0; + if
>> (VIR_ALLOC_N(addrs, i)) + return -1; + + for (i = 0; +
>> (ipdef = virNetworkDefGetIpByIndex(network->def, AF_INET6, i)); +
>> i++) { + addrs[i] = &ipdef->address; + } + + ret =
>> virNetDevWaitDadFinish(addrs, i); + VIR_FREE(addrs); +
>> return ret; +} + +static int
>> networkStartNetworkVirtual(virNetworkDriverStatePtr driver,
>> virNetworkObjPtr network) { @@ -2159,7 +2186,13 @@
>> networkStartNetworkVirtual(virNetworkDriverStatePtr driver, if
>> (v6present && networkStartRadvd(driver, network) < 0) goto err4;
>>
>> - /* DAD has happened (dnsmasq waits for it), dnsmasq is now
>> bound to the + /* dnsmasq main process does not wait for DAD
>> to complete, + * so we need to wait for it ourselves. +
>> */ + if (v6present && networkWaitDadFinish(network) < 0) +
>> goto err4; + + /* DAD has happened, dnsmasq is now bound to
>> the * bridge's IPv6 address, so we can now set the dummy tun
>> down. */ if (tapfd >= 0) { diff --git a/src/util/virnetdev.c
>> b/src/util/virnetdev.c index 1e20789..c81342a 100644 ---
>> a/src/util/virnetdev.c +++ b/src/util/virnetdev.c @@ -96,6 +96,7
>> @@ VIR_LOG_INIT("util.netdev"); # define
>> FEATURE_BIT_IS_SET(blocks, index, field) \
>> (FEATURE_WORD(blocks, index, field) & FEATURE_FIELD_FLAG(index))
>> #endif +# define IP_BUF_SIZE 4096
>>
>> typedef enum { VIR_MCAST_TYPE_INDEX_TOKEN, @@ -1219,6 +1220,103
>> @@ int virNetDevClearIPAddress(const char *ifname, return ret; }
>>
>> +/* return whether there is a known address with 'tentative' flag
>> set */ +static int +virNetDevParseDadStatus(struct nlmsghdr *nlh,
>> int len, + virSocketAddrPtr *addrs, size_t
>> count) +{ + struct ifaddrmsg *ifaddrmsg_ptr; + unsigned int
>> ifaddrmsg_len; + struct rtattr *rtattr_ptr; + size_t i; +
>> struct in6_addr *addr; + for (; NLMSG_OK(nlh, len); nlh =
>> NLMSG_NEXT(nlh, len)) { + if (NLMSG_PAYLOAD(nlh, 0) <
>> sizeof(struct ifaddrmsg)) { + /* Message without
>> payload is the last one. */ + break; + } + +
>> ifaddrmsg_ptr = (struct ifaddrmsg *)NLMSG_DATA(nlh); + if
>> (!(ifaddrmsg_ptr->ifa_flags & IFA_F_TENTATIVE)) { + /*
>> Not tentative: we are not interested in this entry. */ +
>> continue; + } + + ifaddrmsg_len =
>> IFA_PAYLOAD(nlh); + rtattr_ptr = (struct rtattr *)
>> IFA_RTA(ifaddrmsg_ptr); + for (; RTA_OK(rtattr_ptr,
>> ifaddrmsg_len); + rtattr_ptr = RTA_NEXT(rtattr_ptr,
>> ifaddrmsg_len)) { + if (RTA_PAYLOAD(rtattr_ptr) !=
>> sizeof(struct in6_addr)) { + /* No address:
>> ignore. */ + continue; + } + +
>> /* We check only known addresses. */ + for (i = 0; i <
>> count; i++) { + addr =
>> &addrs[i]->data.inet6.sin6_addr; + if
>> (!memcmp(addr, RTA_DATA(rtattr_ptr), +
>> sizeof(struct in6_addr))) { + /* We found
>> matching tentative address. */ + return 1; +
>> } + } + } + } + return 0; +} + +/* return
>> after DAD finishes for all known IPv6 addresses or an error */
>> +int +virNetDevWaitDadFinish(virSocketAddrPtr *addrs, size_t
>> count) +{ + struct nl_msg *nlmsg = NULL; + struct ifaddrmsg
>> ifa; + struct nlmsghdr *resp = NULL; + unsigned int
>> recvbuflen; + int ret = -1, dad = 1; + + if (!(nlmsg =
>> nlmsg_alloc_simple(RTM_GETADDR, +
>> NLM_F_REQUEST | NLM_F_DUMP))) { + virReportOOMError(); +
>> return -1; + } + + memset(&ifa, 0, sizeof(ifa)); + /*
>> DAD is for IPv6 adresses only. */ + ifa.ifa_family =
>> AF_INET6; + if (nlmsg_append(nlmsg, &ifa, sizeof(ifa),
>> NLMSG_ALIGNTO) < 0) { +
>> virReportError(VIR_ERR_INTERNAL_ERROR, "%s", +
>> _("allocated netlink buffer is too small")); + goto
>> cleanup; + } + + /* Periodically query netlink until DAD
>> finishes on all known addresses. */ + while (dad) { +
>> if (virNetlinkCommand(nlmsg, &resp, &recvbuflen, 0, 0, +
>> NETLINK_ROUTE, 0) < 0) + goto cleanup; + + if
>> (virNetlinkGetErrorCode(resp, recvbuflen) < 0) { +
>> virReportError(VIR_ERR_SYSTEM_ERROR, "%s", +
>> _("error reading DAD state information")); + goto
>> cleanup; + } + + /* Parse response. */ + dad
>> = virNetDevParseDadStatus(resp, recvbuflen, addrs, count); +
>> if (dad) + usleep(1000 * 10); + +
>> VIR_FREE(resp); + } + ret = 0; + + cleanup: +
>> VIR_FREE(resp); + nlmsg_free(nlmsg); + return ret; +} +
>> #else /* defined(__linux__) && defined(HAVE_LIBNL) */
>>
>> int virNetDevSetIPAddress(const char *ifname, @@ -1338,6 +1436,68
>> @@ int virNetDevClearIPAddress(const char *ifname, return ret; }
>>
>> +/* return whether there is a known address with 'tentative' flag
>> set */ +static int +virNetDevParseDadStatus(char *outbuf, +
>> virSocketAddrPtr *addrs, size_t count) +{ + virSocketAddr
>> sockaddr; + size_t i, j; + int ret = 0; + char
>> **addr_strings = virStringSplit(outbuf, "\n", 0); + for (j =
>> 0; addr_strings[j] != NULL; ++j) { + if
>> (virSocketParseAddr(strings[j], &sockaddr, AF_INET6) < 0) +
>> continue; + for (i = 0; i < count; i++) { + if
>> (virSocketAddrEqual(addrs[i], &sockaddr)) { + ret
>> = 1; + goto cleanup; + } + } +
>> } + + cleanup: + virStringFreeList(addr_strings); + return
>> ret; +} + +/* return after DAD finishes for all known IPv6
>> addresses or an error */ +int
>> +virNetDevWaitDadFinish(virSocketAddrPtr *addrs, size_t count)
>> +{ + int ret = -1, dad = 1; + char *outbuf = NULL; +
>> virCommandPtr cmd = NULL; + +# ifdef IP_PATH + while (dad) { +
>> cmd = virCommandNew(POSIX_SHELL); +
>> virCommandAddArgList(cmd, "-c", +
>> IP_PATH "-6 addr show tentative | \ +
>> awk '/inet6/{split(\\$2, a, \\\"/\\\"); \ +
>> print a[1]}'", NULL); + virCommandSetOutputBuffer(cmd,
>> &outbuf); + if (virCommandRun(cmd, NULL)) +
>> goto cleanup; + virCommandFree(cmd); + + dad =
>> virNetDevParseDadStatus(outbuf, addrs, count); + if (dad)
>> + usleep(1000 * 10); + + VIR_FREE(outbuf); +
>> } + ret = 0; +# else + virReportSystemError(ENOSYS, "%s",
>> _("Unable to check IPv6 DAD")); +# endif + + cleanup: +
>> virCommandFree(cmd); + VIR_FREE(outbuf); + return ret; +}
>> + #endif /* defined(__linux__) && defined(HAVE_LIBNL) */
>>
>> /** diff --git a/src/util/virnetdev.h b/src/util/virnetdev.h
>> index fff881c..a09b3b2 100644 --- a/src/util/virnetdev.h +++
>> b/src/util/virnetdev.h @@ -105,6 +105,8 @@ int
>> virNetDevClearIPAddress(const char *ifname, ATTRIBUTE_NONNULL(1)
>> ATTRIBUTE_NONNULL(2) ATTRIBUTE_RETURN_CHECK; int
>> virNetDevGetIPAddress(const char *ifname, virSocketAddrPtr addr)
>> ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(2)
>> ATTRIBUTE_RETURN_CHECK; +int
>> virNetDevWaitDadFinish(virSocketAddrPtr *addrs, size_t count) +
>> ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(2);
>>
>>
>> int virNetDevSetMAC(const char *ifname, -- Sincerely, Maxim
>> Perevedentsev
>>
>> -- libvir-list mailing list libvir-list at redhat.com
>> https://www.redhat.com/mailman/listinfo/libvir-list
>>
>
>
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