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LookupServer: Modernize load_etc_hosts()

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This reworks the LookupServer::load_etc_hosts() method to use the
IPv4Address APIs instead of trying to parse an IPv4 address itself.

It also adds a few error checks for invalid entries in /etc/hosts,
trims away leading and trailing whitespace from lines and tries to use
StringView over String.
This commit is contained in:
Max Wipfli 2021-06-07 14:16:57 +02:00 • committed by Ali Mohammad Pur
parent d1dae5f4d1
commit 95d4d36b5c
1 changed files with 30 additions and 25 deletions
Download patch file Download diff file Expand all files Collapse all files

55
Userland/Services/LookupServer/LookupServer.cpp
View file

@ -25,6 +25,8 @@
namespace LookupServer {
static LookupServer* s_the;
// NOTE: This is the TTL we return for the hostname or answers from /etc/hosts.
static constexpr u32 s_static_ttl = 86400;
LookupServer& LookupServer::the()
{
@ -66,48 +68,51 @@ LookupServer::LookupServer()
void LookupServer::load_etc_hosts()
{
// The TTL we return for static data from /etc/hosts.
// The value here is 1 day.
static constexpr u32 static_ttl = 86400;
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()) {
m_etc_hosts.set(name, {});
it = m_etc_hosts.find(name);
}
it->value.empend(name, record_type, DNSRecordClass::IN, static_ttl, data, false);
it->value.empend(name, record_type, DNSRecordClass::IN, s_static_ttl, data, false);
};
auto file = Core::File::construct("/etc/hosts");
if (!file->open(Core::OpenMode::ReadOnly))
if (!file->open(Core::OpenMode::ReadOnly)) {
dbgln("Failed to open '/etc/hosts'");
return;
}
u32 line_number = 0;
while (!file->eof()) {
auto line = file->read_line(1024);
if (line.is_empty())
auto original_line = file->read_line(1024);
++line_number;
if (original_line.is_empty())
break;
auto fields = line.split('\t');
auto trimmed_line = original_line.view().trim_whitespace();
auto fields = trimmed_line.split_view('\t', false);
auto sections = fields[0].split('.');
IPv4Address addr {
(u8)atoi(sections[0].characters()),
(u8)atoi(sections[1].characters()),
(u8)atoi(sections[2].characters()),
(u8)atoi(sections[3].characters()),
};
auto raw_addr = addr.to_in_addr_t();
if (fields.size() < 2) {
dbgln("Failed to parse line {} from '/etc/hosts': '{}'", line_number, original_line);
continue;
}
DNSName name = fields[1];
if (fields.size() > 2)
dbgln("Line {} from '/etc/hosts' ('{}') has more than two parts, only the first two are used.", line_number, original_line);
auto maybe_address = IPv4Address::from_string(fields[0]);
if (!maybe_address.has_value()) {
dbgln("Failed to parse line {} from '/etc/hosts': '{}'", line_number, original_line);
continue;
}
auto raw_addr = maybe_address->to_in_addr_t();
DNSName name { fields[1] };
add_answer(name, DNSRecordType::A, String { (const char*)&raw_addr, sizeof(raw_addr) });
IPv4Address reverse_addr {
(u8)atoi(sections[3].characters()),
(u8)atoi(sections[2].characters()),
(u8)atoi(sections[1].characters()),
(u8)atoi(sections[0].characters()),
};
StringBuilder builder;
builder.append(reverse_addr.to_string());
builder.append(maybe_address->to_string_reversed());
builder.append(".in-addr.arpa");
add_answer(builder.to_string(), DNSRecordType::PTR, name.as_string());
}