Bananymous/banan-os
1
1
Fork 1
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Userspace: Add DNS cache to resolver

Browse Source 
Also the format of resolver reply is now just sockaddr_storage with
family set and address in the storage field.
This commit is contained in:
Bananymous
2024-02-08 12:03:54 +02:00
parent 6fb69a1dc2
commit 065ee9004c
2 changed files with 73 additions and 23 deletions
Download Patch File Download Diff File Expand all files Collapse all files

79
userspace/resolver/main.cpp
View File

@@ -39,6 +39,19 @@ struct DNSAnswer
};
static_assert(sizeof(DNSAnswer) == 12);
enum QTYPE : uint16_t
{
A = 0x0001,
CNAME = 0x0005,
AAAA = 0x001C,
};
struct DNSEntry
{
time_t valid_until { 0 };
BAN::IPv4Address address { 0 };
};
bool send_dns_query(int socket, BAN::StringView domain, uint16_t id)
{
static uint8_t buffer[4096];
@@ -61,8 +74,8 @@ bool send_dns_query(int socket, BAN::StringView domain, uint16_t id)
}
request.data[idx++] = 0x00;
*(uint16_t*)&request.data[idx] = htons(0x01); idx += 2;
*(uint16_t*)&request.data[idx] = htons(0x01); idx += 2;
*(uint16_t*)&request.data[idx] = htons(QTYPE::A); idx += 2;
*(uint16_t*)&request.data[idx] = htons(0x0001); idx += 2;
sockaddr_in nameserver;
nameserver.sin_family = AF_INET;
@@ -77,7 +90,7 @@ bool send_dns_query(int socket, BAN::StringView domain, uint16_t id)
return true;
}
BAN::Optional<BAN::String> read_dns_response(int socket, uint16_t id)
BAN::Optional<DNSEntry> read_dns_response(int socket, uint16_t id)
{
static uint8_t buffer[4096];
@@ -109,13 +122,22 @@ BAN::Optional<BAN::String> read_dns_response(int socket, uint16_t id)
}
DNSAnswer& answer = *reinterpret_cast<DNSAnswer*>(&reply.data[idx]);
if (answer.type() != QTYPE::A)
{
fprintf(stderr, "Not A record\n");
return {};
}
if (answer.data_len() != 4)
{
fprintf(stderr, "Not IPv4\n");
fprintf(stderr, "corrupted package\n");
return {};
}
return inet_ntoa({ .s_addr = *reinterpret_cast<uint32_t*>(answer.data) });
DNSEntry result;
result.valid_until = time(nullptr) + answer.ttl();
result.address = BAN::IPv4Address(*reinterpret_cast<uint32_t*>(answer.data));
return result;
}
int create_service_socket()
@@ -182,6 +204,8 @@ int main(int, char**)
return 1;
}
BAN::HashMap<BAN::String, DNSEntry> dns_cache;
for (;;)
{
int client = accept(service_socket, nullptr, nullptr);
@@ -193,24 +217,43 @@ int main(int, char**)
auto query = read_service_query(client);
if (!query.has_value())
continue;
uint16_t id = rand() % 0xFFFF;
if (send_dns_query(dns_socket, *query, id))
{
auto response = read_dns_response(dns_socket, id);
if (response.has_value())
close(client);
continue;
}
BAN::Optional<DNSEntry> result;
if (dns_cache.contains(*query))
{
auto& cached = dns_cache[*query];
if (time(nullptr) <= cached.valid_until)
result = cached;
else
dns_cache.remove(*query);
}
if (!result.has_value())
{
uint16_t id = rand() % 0xFFFF;
if (send_dns_query(dns_socket, *query, id))
{
if (send(client, response->data(), response->size() + 1, 0) == -1)
perror("send");
close(client);
continue;
result = read_dns_response(dns_socket, id);
if (result.has_value())
(void)dns_cache.insert(*query, *result);
}
}
char message[] = "unavailable";
send(client, message, sizeof(message), 0);
if (!result.has_value())
result = DNSEntry { .valid_until = 0, .address = BAN::IPv4Address(INADDR_ANY) };
sockaddr_storage storage;
storage.ss_family = AF_INET;
memcpy(storage.ss_storage, &result->address.raw, sizeof(result->address.raw));
if (send(client, &storage, sizeof(storage), 0) == -1)
perror("send");
close(client);
}