On Wed, Nov 23, 2016 at 3:27 PM, Justin Cinkelj <justin.cink...@xlab.si>
wrote:
> When cloud-init changes VM hostname, VM DNS name should be updated too.
> We try to do this by releasing DHCP lease and requesting new lease
> with new name. This instructs DHCP server to perform dynamic DNS update.
> DNS update will/should succeed if
> 1) new name is not already claimed by some other VM/IP and
> 2) obviously, DHCP and DNS server need to support dynamic DNS updates.
>
> The dhcp_worker::init was split into two parts (::init and ::start), so
> that can be discovery-resend logic can be reused.
>
> Signed-off-by: Justin Cinkelj <justin.cink...@xlab.si>
> ---
> core/dhcp.cc | 23 ++++++++++++++++++-----
> include/osv/dhcp.hh | 8 ++++++--
> modules/cloud-init/cloud-init.cc | 27 +++++++++++++++++++--------
> 3 files changed, 43 insertions(+), 15 deletions(-)
>
> diff --git a/core/dhcp.cc b/core/dhcp.cc
> index 27d7aef..d89eb46 100644
> --- a/core/dhcp.cc
> +++ b/core/dhcp.cc
> @@ -66,7 +66,8 @@ int dhcp_hook_rx(struct mbuf* m)
> void dhcp_start(bool wait)
> {
> // Initialize the global DHCP worker
> - net_dhcp_worker.init(wait);
> + net_dhcp_worker.init();
> + net_dhcp_worker.start(wait);
> }
>
> // Send DHCP release, for example at shutdown.
> @@ -75,6 +76,12 @@ void dhcp_release()
> net_dhcp_worker.release();
> }
>
> +void dhcp_restart(bool wait)
> +{
> + net_dhcp_worker.release();
> + net_dhcp_worker.start(wait);
> +}
> +
> namespace dhcp {
>
> const char * dhcp_options_magic = "\x63\x82\x53\x63";
> @@ -504,7 +511,10 @@ namespace dhcp {
>
> void dhcp_interface_state::discover()
> {
> - // FIXME: send release packet in case the interface has an address
> + // send release packet in case the interface has an address
> + if (_client_addr != ipv4_zero) {
> + release();
> + }
>
I don't know why this FIXME was correct, or why this extra code was needed:
In both the dhcp_start() and dhcp_restart() cases, we start with zero
address (in dhcp_restart() you call release() already). So why do we need
to check it again here?
>
> // Update state
> _state = DHCP_DISCOVER;
> @@ -665,12 +675,10 @@ namespace dhcp {
> // FIXME: free packets and states
> }
>
> - void dhcp_worker::init(bool wait)
> + void dhcp_worker::init()
> {
> struct ifnet *ifp = nullptr;
>
> - // FIXME: clear routing table (use case run dhclient 2nd time)
> -
> // Allocate a state for each interface
> IFNET_RLOCK();
> TAILQ_FOREACH(ifp, &V_ifnet, if_link) {
> @@ -686,7 +694,11 @@ namespace dhcp {
> _dhcp_thread = sched::thread::make([&] { dhcp_worker_fn(); });
> _dhcp_thread->set_name("dhcp");
> _dhcp_thread->start();
> + }
>
> + void dhcp_worker::start(bool wait)
> + {
> + // FIXME: clear routing table (use case run dhclient 2nd time)
> do {
> // Send discover packets!
> for (auto &it: _universe) {
> @@ -711,6 +723,7 @@ namespace dhcp {
> for (auto &it: _universe) {
> it.second->release();
> }
> + _have_ip = false;
> // Wait a bit, so hopefully UDP release packets will be actually
> put on wire.
> usleep(1000);
> }
> diff --git a/include/osv/dhcp.hh b/include/osv/dhcp.hh
> index 30ca86f..b286727 100644
> --- a/include/osv/dhcp.hh
> +++ b/include/osv/dhcp.hh
> @@ -25,6 +25,7 @@
> extern "C" {
> void dhcp_start(bool wait);
> void dhcp_release();
> +void dhcp_restart(bool wait);
> }
>
> namespace dhcp {
> @@ -249,8 +250,11 @@ namespace dhcp {
> dhcp_worker();
> ~dhcp_worker();
>
> - // Initializing a state per interface, sends discover packets
> - void init(bool wait);
> + // Initializing a state per interface
> + void init();
> + // Send discover packets
> + void start(bool wait);
> + // Send release packet for all DHCP IPs.
> void release();
>
> void dhcp_worker_fn();
> diff --git a/modules/cloud-init/cloud-init.cc b/modules/cloud-init/cloud-
> init.cc
> index 67f477e..e3ec8f8 100644
> --- a/modules/cloud-init/cloud-init.cc
> +++ b/modules/cloud-init/cloud-init.cc
> @@ -16,6 +16,22 @@
> #include <osv/firmware.hh>
> #include <osv/hypervisor.hh>
>
> +// we cannot include osv/dhcp.hh, hence direct declaration.
> +extern "C" void dhcp_restart(bool wait);
> +
> +// Set the hostname to given string.
> +// If hostname changes, try to propagate the change to DHCP server too.
> +void set_hostname_restart_dhcp(std::string hostname) {
> + if (hostname.length() > 0) {
> + char old_hostname[256] = "";
> + gethostname(old_hostname, sizeof(old_hostname));
> + sethostname(hostname.c_str(), hostname.length());
> + if (hostname != old_hostname) {
> + dhcp_restart(true);
> + }
> + }
> +}
> +
> namespace init {
> using namespace std;
>
> @@ -229,9 +245,7 @@ void hostname_module::handle(const YAML::Node& doc)
> {
> auto hostname = doc.as<string>();
> debug("cloudinit hostname: %s\n", hostname.c_str());
> - if (hostname.size()) {
> - sethostname(hostname.c_str(), hostname.size());
> - }
> + set_hostname_restart_dhcp(hostname);
> }
>
> void osvinit::add_module(std::shared_ptr<config_module> module)
> @@ -265,11 +279,8 @@ void osvinit::load_from_cloud(bool
> ignore_missing_source)
> try {
> auto& ds = get_data_source();
>
> - std::string hostname = ds.external_hostname();
> - if (hostname.length() > 0) {
> - // Set the hostname from given data source, if it exists.
> - sethostname(hostname.c_str(), hostname.length());
> - }
> + // Set the hostname from given data source, if it exists.
> + set_hostname_restart_dhcp(ds.external_hostname());
>
> // Load user data.
> user_data = ds.get_user_data();
> --
> 2.9.3
>
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