[libc-commits] [libc] [libc] Read multiple interfaces per netlink message in if_nameindex (PR #213952)

[Pavel Labath via libc-commits]

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@@ -60,38 +61,19 @@ LIBC_INLINE ErrorOr<ssize_t> send_netlink_dump_request(int sockfd) {
 /// A reasonable buffer size for netlink messages (see NLMSG_GOODSIZE in the
 /// kernel).
 constexpr size_t NLMSG_BUFFER_SIZE = 8192;
-} // namespace detail
-
-template <typename Policy>
-LIBC_INLINE ErrorOr<struct if_nameindex *> if_nameindex() {
-  ErrorOr<int> fd_or_err =
-      Policy::socket(AF_NETLINK, SOCK_RAW | SOCK_CLOEXEC, NETLINK_ROUTE);
-  if (!fd_or_err.has_value())
-    return Error(fd_or_err.error());
-  int fd = *fd_or_err;
-  cpp::scope_exit close_fd([fd]() { Policy::close(fd); });
-
-  ErrorOr<ssize_t> send_res = detail::send_netlink_dump_request<Policy>(fd);
-  if (!send_res.has_value())
-    return Error(send_res.error());
-
-  // TODO: Figure out if we need to dynamically allocate a buffer.
-  alignas(struct nlmsghdr) uint8_t buf[detail::NLMSG_BUFFER_SIZE];
-  ErrorOr<ssize_t> recv_res =
-      Policy::recvfrom(fd, buf, sizeof(buf), 0, nullptr, nullptr);
-  if (!recv_res.has_value())
-    return Error(recv_res.error());
 
-  close_fd.release();
-  if (ErrorOr<int> close_res = Policy::close(fd); !close_res.has_value())
-    return Error(close_res.error());
-
-  // TODO: Read more than one message.
-  // TODO: Read more than one interface per message.
-  // TODO: Deduplicate interfaces to handle restarts.
-  auto len = static_cast<size_t>(*recv_res);
-  for (auto *nh = reinterpret_cast<struct nlmsghdr *>(buf); NLMSG_OK(nh, len);
-       nh = NLMSG_NEXT(nh, len)) {
+struct InterfaceEntry {
+  unsigned int index;
+  char name[IF_NAMESIZE];
+};
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labath wrote:

Not if it increases the size of the structure, but I think I've managed to create a pretty clean solution that replaces the null terminator byte with a size field (same memory footprint, but two strlen calls less).

https://github.com/llvm/llvm-project/pull/213952