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LookupServer: Watch /etc/hosts for changes during runtime

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This adds a FileWatcher to the LookupServer which watches '/etc/hosts'
for changes during runtime and reloads its contents. If the file is
deleted, m_etc_hosts will be cleared.

Since we now need to access '/etc/hosts' later during runtime, it needs
to be unveiled with read permissions.
This commit is contained in:
Max Wipfli 2021-06-07 20:26:09 +02:00 • committed by Ali Mohammad Pur
parent 7b39db3bf4
commit 4efccbd030
3 changed files with 31 additions and 0 deletions
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24
Userland/Services/LookupServer/LookupServer.cpp
View file

@ -45,6 +45,29 @@ LookupServer::LookupServer()
load_etc_hosts();
auto maybe_file_watcher = Core::FileWatcher::create();
// NOTE: If this happens during startup, something is very wrong.
if (maybe_file_watcher.is_error()) {
dbgln("Core::FileWatcher::create(): {}", maybe_file_watcher.error());
VERIFY_NOT_REACHED();
}
m_file_watcher = maybe_file_watcher.release_value();
m_file_watcher->on_change = [this](auto&) {
dbgln("Reloading '/etc/hosts' because it was changed.");
load_etc_hosts();
};
auto result = m_file_watcher->add_watch("/etc/hosts", Core::FileWatcherEvent::Type::ContentModified | Core::FileWatcherEvent::Type::Deleted);
// NOTE: If this happens during startup, something is very wrong.
if (result.is_error()) {
dbgln("Core::FileWatcher::add_watch(): {}", result.error());
VERIFY_NOT_REACHED();
} else if (!result.value()) {
dbgln("Core::FileWatcher::add_watch(): {}", result.value());
VERIFY_NOT_REACHED();
}
if (config->read_bool_entry("DNS", "EnableServer")) {
m_dns_server = DNSServer::construct(this);
// TODO: drop root privileges here.
@ -68,6 +91,7 @@ LookupServer::LookupServer()
void LookupServer::load_etc_hosts()
{
m_etc_hosts.clear();
auto add_answer = [this](const DNSName& name, DNSRecordType record_type, String data) {
auto it = m_etc_hosts.find(name);
if (it == m_etc_hosts.end()) {

2
Userland/Services/LookupServer/LookupServer.h
View file

@ -10,6 +10,7 @@
#include "DNSPacket.h"
#include "DNSServer.h"
#include "MulticastDNS.h"
#include <LibCore/FileWatcher.h>
#include <LibCore/Object.h>
namespace LookupServer {
@ -35,6 +36,7 @@ private:
RefPtr<DNSServer> m_dns_server;
RefPtr<MulticastDNS> m_mdns;
Vector<String> m_nameservers;
RefPtr<Core::FileWatcher> m_file_watcher;
HashMap<DNSName, Vector<DNSAnswer>, DNSName::Traits> m_etc_hosts;
HashMap<DNSName, Vector<DNSAnswer>, DNSName::Traits> m_lookup_cache;
};

5
Userland/Services/LookupServer/main.cpp
View file

@ -30,6 +30,11 @@ int main([[maybe_unused]] int argc, [[maybe_unused]] char** argv)
return 1;
}
if (unveil("/etc/hosts", "r") < 0) {
perror("unveil");
return 1;
}
if (unveil(nullptr, nullptr) < 0) {
perror("unveil");
return 1;