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LibC: Use gethostbyname_r() in gethostbyname()

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Since `gethostbyname()` can't fail because of memory-related issues, it
has no way of representing a memory-related failure. We therefor use
`NO_RECOVERY` to represent a memory-related failure as well
as its normal name server related failures.
This commit is contained in:
Marcus Nilsson 2023-08-16 22:48:42 +02:00 • committed by Andrew Kaster
parent 5c4b71ac67
commit fd792f93c4
1 changed files with 26 additions and 97 deletions
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123
Userland/Libraries/LibC/netdb.cpp
View file

@ -93,108 +93,36 @@ static DeprecatedString gethostbyname_name_buffer;
hostent* gethostbyname(char const* name)
{
h_errno = 0;
struct hostent ret = {};
struct hostent* result = nullptr;
size_t buffer_size = 1024;
char* buffer = nullptr;
auto ipv4_address = IPv4Address::from_string({ name, strlen(name) });
if (ipv4_address.has_value()) {
gethostbyname_name_buffer = ipv4_address.value().to_deprecated_string();
__gethostbyname_buffer.h_name = const_cast<char*>(gethostbyname_name_buffer.characters());
__gethostbyname_alias_list_buffer[0] = nullptr;
__gethostbyname_buffer.h_aliases = __gethostbyname_alias_list_buffer;
__gethostbyname_buffer.h_addrtype = AF_INET;
new (&__gethostbyname_address) IPv4Address(ipv4_address.value());
__gethostbyname_address_list_buffer[0] = &__gethostbyname_address;
__gethostbyname_address_list_buffer[1] = nullptr;
__gethostbyname_buffer.h_addr_list = (char**)__gethostbyname_address_list_buffer;
__gethostbyname_buffer.h_length = 4;
return &__gethostbyname_buffer;
}
int fd = connect_to_lookup_server();
if (fd < 0) {
h_errno = TRY_AGAIN;
return nullptr;
}
auto close_fd_on_exit = ScopeGuard([fd] {
close(fd);
auto free_buffer_on_exit = ScopeGuard([buffer] {
if (buffer != nullptr)
free(buffer);
});
auto name_length = strlen(name);
VERIFY(name_length <= NumericLimits<i32>::max());
while (true) {
buffer = (char*)realloc(buffer, buffer_size);
if (buffer == nullptr) {
// NOTE: Since gethostbyname usually can't fail because of memory,
// it has no way of representing OOM or allocation failure.
// NO_RECOVERY is the next best thing.
h_errno = NO_RECOVERY;
return NULL;
}
struct [[gnu::packed]] {
u32 message_size;
u32 endpoint_magic;
i32 message_id;
u32 name_length;
} request_header = {
(u32)(sizeof(request_header) - sizeof(request_header.message_size) + name_length),
lookup_server_endpoint_magic,
1,
static_cast<u32>(name_length),
};
if (auto nsent = write(fd, &request_header, sizeof(request_header)); nsent < 0) {
h_errno = TRY_AGAIN;
return nullptr;
} else if (nsent != sizeof(request_header)) {
h_errno = NO_RECOVERY;
return nullptr;
}
int rc = gethostbyname_r(name, &ret, buffer, buffer_size, &result, &h_errno);
if (rc == ERANGE) {
buffer_size *= 2;
continue;
}
if (auto nsent = write(fd, name, name_length); nsent < 0) {
h_errno = TRY_AGAIN;
return nullptr;
} else if (static_cast<size_t>(nsent) != name_length) {
h_errno = NO_RECOVERY;
return nullptr;
}
if (rc < 0)
return nullptr;
struct [[gnu::packed]] {
u32 message_size;
u32 endpoint_magic;
i32 message_id;
i32 code;
u32 addresses_count;
} response_header;
if (auto nreceived = read(fd, &response_header, sizeof(response_header)); nreceived < 0) {
h_errno = TRY_AGAIN;
return nullptr;
} else if (nreceived != sizeof(response_header)) {
h_errno = NO_RECOVERY;
return nullptr;
}
if (response_header.endpoint_magic != lookup_server_endpoint_magic || response_header.message_id != 2) {
h_errno = NO_RECOVERY;
return nullptr;
}
if (response_header.code != 0) {
h_errno = NO_RECOVERY;
return nullptr;
}
if (response_header.addresses_count == 0) {
h_errno = HOST_NOT_FOUND;
return nullptr;
}
i32 response_length;
if (auto nreceived = read(fd, &response_length, sizeof(response_length)); nreceived < 0) {
h_errno = TRY_AGAIN;
return nullptr;
} else if (nreceived != sizeof(response_length)
|| response_length != sizeof(__gethostbyname_address)) {
h_errno = NO_RECOVERY;
return nullptr;
}
if (auto nreceived = read(fd, &__gethostbyname_address, response_length); nreceived < 0) {
h_errno = TRY_AGAIN;
return nullptr;
} else if (nreceived != response_length) {
h_errno = NO_RECOVERY;
return nullptr;
break;
}
gethostbyname_name_buffer = name;
@ -202,10 +130,11 @@ hostent* gethostbyname(char const* name)
__gethostbyname_alias_list_buffer[0] = nullptr;
__gethostbyname_buffer.h_aliases = __gethostbyname_alias_list_buffer;
__gethostbyname_buffer.h_addrtype = AF_INET;
memcpy(&__gethostbyname_address, result->h_addr_list[0], sizeof(in_addr_t));
__gethostbyname_address_list_buffer[0] = &__gethostbyname_address;
__gethostbyname_address_list_buffer[1] = nullptr;
__gethostbyname_buffer.h_addr_list = (char**)__gethostbyname_address_list_buffer;
__gethostbyname_buffer.h_length = 4;
__gethostbyname_buffer.h_length = result->h_length;
return &__gethostbyname_buffer;
}