From: Justin Cinkelj <justin.cink...@xlab.si>
Committer: Nadav Har'El <n...@scylladb.com>
Branch: master
cloud-init: trigger dynamic DNS update on hostname change
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>
Message-Id: <20161123144311.29393-1-justin.cink...@xlab.si>
---
diff --git a/core/dhcp.cc b/core/dhcp.cc
--- 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";
@@ -504,8 +511,6 @@ namespace dhcp {
void dhcp_interface_state::discover()
{
- // FIXME: send release packet in case the interface has an address
-
// Update state
_state = DHCP_DISCOVER;
@@ -665,12 +670,10 @@ 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 +689,11 @@ 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 +718,7 @@ 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
--- 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
--- 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();
--
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