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LibC: Try to recover gracefully from failed LookupServer requests

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gethostbyname() and gethostbyaddr() now set h_errno (per spec) and try
to recover and return (with an error) instead of choking in VERIFY()
whenever an I/O or protocol error occurs in the communication with
LookupServer.
This commit is contained in:
Andreas Kling 2022-02-16 11:39:23 +01:00
parent 083b58fd89
commit 5caeb8b747
1 changed files with 73 additions and 52 deletions
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125
Userland/Libraries/LibC/netdb.cpp
View file

@ -87,6 +87,8 @@ static String gethostbyname_name_buffer;
hostent* gethostbyname(const char* name) hostent* gethostbyname(const char* name)
{ {
h_errno = 0;
auto ipv4_address = IPv4Address::from_string(name); auto ipv4_address = IPv4Address::from_string(name);
if (ipv4_address.has_value()) { if (ipv4_address.has_value()) {
@ -104,14 +106,18 @@ hostent* gethostbyname(const char* name)
} }
int fd = connect_to_lookup_server(); int fd = connect_to_lookup_server();
if (fd < 0) if (fd < 0) {
h_errno = TRY_AGAIN;
return nullptr; return nullptr;
}
auto close_fd_on_exit = ScopeGuard([fd] { auto close_fd_on_exit = ScopeGuard([fd] {
close(fd); close(fd);
}); });
size_t name_length = strlen(name); size_t unsigned_name_length = strlen(name);
VERIFY(unsigned_name_length <= NumericLimits<i32>::max());
i32 name_length = static_cast<i32>(unsigned_name_length);
struct [[gnu::packed]] { struct [[gnu::packed]] {
u32 message_size; u32 message_size;
@ -122,20 +128,23 @@ hostent* gethostbyname(const char* name)
(u32)(sizeof(request_header) - sizeof(request_header.message_size) + name_length), (u32)(sizeof(request_header) - sizeof(request_header.message_size) + name_length),
lookup_server_endpoint_magic, lookup_server_endpoint_magic,
1, 1,
(i32)name_length, name_length,
}; };
int nsent = write(fd, &request_header, sizeof(request_header)); if (auto nsent = write(fd, &request_header, sizeof(request_header)); nsent < 0) {
if (nsent < 0) { h_errno = TRY_AGAIN;
perror("write"); return nullptr;
} else if (nsent != sizeof(request_header)) {
h_errno = NO_RECOVERY;
return nullptr; return nullptr;
} }
VERIFY((size_t)nsent == sizeof(request_header));
nsent = write(fd, name, name_length); if (auto nsent = write(fd, name, name_length); nsent < 0) {
if (nsent < 0) { h_errno = TRY_AGAIN;
perror("write"); return nullptr;
} else if (nsent != name_length) {
h_errno = NO_RECOVERY;
return nullptr; return nullptr;
} }
VERIFY((size_t)nsent == name_length);
struct [[gnu::packed]] { struct [[gnu::packed]] {
u32 message_size; u32 message_size;
@ -145,37 +154,42 @@ hostent* gethostbyname(const char* name)
u64 addresses_count; u64 addresses_count;
} response_header; } response_header;
int nrecv = read(fd, &response_header, sizeof(response_header)); if (auto nreceived = read(fd, &response_header, sizeof(response_header)); nreceived < 0) {
if (nrecv < 0) { h_errno = TRY_AGAIN;
perror("recv"); return nullptr;
} else if (nreceived != sizeof(response_header)) {
h_errno = NO_RECOVERY;
return nullptr; return nullptr;
} }
VERIFY((size_t)nrecv == sizeof(response_header));
if (response_header.endpoint_magic != lookup_server_endpoint_magic || response_header.message_id != 2) { if (response_header.endpoint_magic != lookup_server_endpoint_magic || response_header.message_id != 2) {
dbgln("Received an unexpected message"); h_errno = NO_RECOVERY;
return nullptr; return nullptr;
} }
if (response_header.code != 0) { if (response_header.code != 0) {
// TODO: return a specific error. h_errno = NO_RECOVERY;
return nullptr;
}
if (response_header.addresses_count == 0) {
h_errno = HOST_NOT_FOUND;
return nullptr; return nullptr;
} }
VERIFY(response_header.addresses_count > 0);
i32 response_length; i32 response_length;
nrecv = read(fd, &response_length, sizeof(response_length)); if (auto nreceived = read(fd, &response_length, sizeof(response_length)); nreceived < 0) {
if (nrecv < 0) { h_errno = TRY_AGAIN;
perror("recv"); return nullptr;
} else if (nreceived != sizeof(response_length)
|| response_length != sizeof(__gethostbyname_address)) {
h_errno = NO_RECOVERY;
return nullptr; return nullptr;
} }
VERIFY((size_t)nrecv == sizeof(response_length));
VERIFY(response_length == sizeof(__gethostbyname_address));
nrecv = read(fd, &__gethostbyname_address, response_length); if (auto nreceived = read(fd, &__gethostbyname_address, response_length); nreceived < 0) {
if (nrecv < 0) { h_errno = TRY_AGAIN;
perror("recv"); return nullptr;
} else if (nreceived != response_length) {
h_errno = NO_RECOVERY;
return nullptr; return nullptr;
} }
VERIFY(nrecv == response_length);
gethostbyname_name_buffer = name; gethostbyname_name_buffer = name;
__gethostbyname_buffer.h_name = const_cast<char*>(gethostbyname_name_buffer.characters()); __gethostbyname_buffer.h_name = const_cast<char*>(gethostbyname_name_buffer.characters());
@ -193,6 +207,8 @@ static String gethostbyaddr_name_buffer;
hostent* gethostbyaddr(const void* addr, socklen_t addr_size, int type) hostent* gethostbyaddr(const void* addr, socklen_t addr_size, int type)
{ {
h_errno = 0;
if (type != AF_INET) { if (type != AF_INET) {
errno = EAFNOSUPPORT; errno = EAFNOSUPPORT;
return nullptr; return nullptr;
@ -204,8 +220,10 @@ hostent* gethostbyaddr(const void* addr, socklen_t addr_size, int type)
} }
int fd = connect_to_lookup_server(); int fd = connect_to_lookup_server();
if (fd < 0) if (fd < 0) {
h_errno = TRY_AGAIN;
return nullptr; return nullptr;
}
auto close_fd_on_exit = ScopeGuard([fd] { auto close_fd_on_exit = ScopeGuard([fd] {
close(fd); close(fd);
@ -222,20 +240,22 @@ hostent* gethostbyaddr(const void* addr, socklen_t addr_size, int type)
sizeof(request_header) - sizeof(request_header.message_size) + sizeof(in_addr), sizeof(request_header) - sizeof(request_header.message_size) + sizeof(in_addr),
lookup_server_endpoint_magic, lookup_server_endpoint_magic,
3, 3,
(i32)sizeof(in_addr), sizeof(in_addr),
}; };
int nsent = write(fd, &request_header, sizeof(request_header)); if (auto nsent = write(fd, &request_header, sizeof(request_header)); nsent < 0) {
if (nsent < 0) { h_errno = TRY_AGAIN;
perror("write"); return nullptr;
} else if (nsent != sizeof(request_header)) {
h_errno = NO_RECOVERY;
return nullptr; return nullptr;
} }
VERIFY((size_t)nsent == sizeof(request_header)); if (auto nsent = write(fd, &in_addr, sizeof(in_addr)); nsent < 0) {
nsent = write(fd, &in_addr, sizeof(in_addr)); h_errno = TRY_AGAIN;
if (nsent < 0) { return nullptr;
perror("write"); } else if (nsent != sizeof(in_addr)) {
h_errno = TRY_AGAIN;
return nullptr; return nullptr;
} }
VERIFY((size_t)nsent == sizeof(in_addr));
struct [[gnu::packed]] { struct [[gnu::packed]] {
u32 message_size; u32 message_size;
@ -245,29 +265,30 @@ hostent* gethostbyaddr(const void* addr, socklen_t addr_size, int type)
i32 name_length; i32 name_length;
} response_header; } response_header;
int nrecv = read(fd, &response_header, sizeof(response_header)); if (auto nreceived = read(fd, &response_header, sizeof(response_header)); nreceived < 0) {
if (nrecv < 0) { h_errno = TRY_AGAIN;
perror("recv"); return nullptr;
} else if (nreceived != sizeof(response_header)) {
h_errno = NO_RECOVERY;
return nullptr; return nullptr;
} }
VERIFY((size_t)nrecv == sizeof(response_header)); if (response_header.endpoint_magic != lookup_server_endpoint_magic
if (response_header.endpoint_magic != lookup_server_endpoint_magic || response_header.message_id != 4) { || response_header.message_id != 4
dbgln("Received an unexpected message"); || response_header.code != 0) {
return nullptr; h_errno = NO_RECOVERY;
}
if (response_header.code != 0) {
// TODO: return a specific error.
return nullptr; return nullptr;
} }
char* buffer; char* buffer;
auto string_impl = StringImpl::create_uninitialized(response_header.name_length, buffer); auto string_impl = StringImpl::create_uninitialized(response_header.name_length, buffer);
nrecv = read(fd, buffer, response_header.name_length);
if (nrecv < 0) { if (auto nreceived = read(fd, buffer, response_header.name_length); nreceived < 0) {
perror("recv"); h_errno = TRY_AGAIN;
return nullptr;
} else if (nreceived != response_header.name_length) {
h_errno = NO_RECOVERY;
return nullptr; return nullptr;
} }
VERIFY(nrecv == response_header.name_length);
gethostbyaddr_name_buffer = move(string_impl); gethostbyaddr_name_buffer = move(string_impl);
__gethostbyaddr_buffer.h_name = buffer; __gethostbyaddr_buffer.h_name = buffer;