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// Copyright (C) 2019-2024 Algorand, Inc.
// This file is part of go-algorand
//
// go-algorand is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as
// published by the Free Software Foundation, either version 3 of the
// License, or (at your option) any later version.
//
// go-algorand is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with go-algorand. If not, see <https://www.gnu.org/licenses/>.
//go:build windows
// +build windows
package dnssec
import (
"fmt"
"time"
"unsafe"
"golang.org/x/sys/windows"
)
var (
dll = windows.NewLazyDLL("iphlpapi.dll")
networkParamsProc = dll.NewProc("GetNetworkParams")
)
// values from https://referencesource.microsoft.com/#System/net/System/Net/NetworkInformation/UnSafeNetInfoNativemethods.cs,c5dd09342271faba,references
const (
max_hostname_len = 128
max_domain_name_len = 128
max_scope_id_len = 256
)
const ip_size = 16
// typedef struct _IP_ADDR_STRING {
// struct _IP_ADDR_STRING *Next;
// IP_ADDRESS_STRING IpAddress; // The String member is a char array of size 16. This array holds an IPv4 address in dotted decimal notation.
// IP_MASK_STRING IpMask; // The String member is a char array of size 16. This array holds the IPv4 subnet mask in dotted decimal notation.
// DWORD Context;
// } IP_ADDR_STRING, *PIP_ADDR_STRING;
//
// https://docs.microsoft.com/en-us/windows/win32/api/iptypes/ns-iptypes-ip_addr_string
type ipAddrString struct {
Next uintptr
IpAddress [ip_size]uint8
IpMask [ip_size]uint8
Context uint32
}
// typedef struct {
// char HostName[MAX_HOSTNAME_LEN + 4];
// char DomainName[MAX_DOMAIN_NAME_LEN + 4];
// PIP_ADDR_STRING CurrentDnsServer;
// IP_ADDR_STRING DnsServerList;
// UINT NodeType;
// char ScopeId[MAX_SCOPE_ID_LEN + 4];
// UINT EnableRouting;
// UINT EnableProxy;
// UINT EnableDns;
// } FIXED_INFO_W2KSP1, *PFIXED_INFO_W2KSP1;
//
// https://docs.microsoft.com/en-us/windows/win32/api/iptypes/ns-iptypes-fixed_info_w2ksp1
type fixedInfo struct {
HostName [max_hostname_len + 4]uint8
DomainName [max_domain_name_len + 4]uint8
CurrentDnsServer uintptr
DnsServerList ipAddrString
NodeType uint32
ScopeId [max_scope_id_len + 4]uint8
EnableRouting uint32
EnableProxy uint32
EnableDns uint32
}
const ipAddrStringSizeof = 48
type fixedInfoWithOverlay struct {
fixedInfo
overlay [ipAddrStringSizeof * 32]uint8 // space for max 32 IP_ADDR_STRING entries in the overlay
}
// SystemConfig return list of DNS servers from Windows configuration
//
// See GetNetworkParams for details:
// https://docs.microsoft.com/en-us/windows/win32/api/iphlpapi/nf-iphlpapi-getnetworkparams
func SystemConfig() (servers []ResolverAddress, timeout time.Duration, err error) {
ulSize := uint32(unsafe.Sizeof(fixedInfoWithOverlay{}))
buf, err := windows.LocalAlloc(windows.LMEM_FIXED|windows.LMEM_ZEROINIT, ulSize)
if err != nil {
err = fmt.Errorf("GetNetworkParams failed to allocate %d bytes of memory for fixedInfoWithOverlay", ulSize)
return
}
defer windows.LocalFree(windows.Handle(buf))
ret, _, _ := networkParamsProc.Call(
buf,
uintptr(unsafe.Pointer(&ulSize)),
)
if ret != 0 {
if windows.Errno(ret) == windows.ERROR_BUFFER_OVERFLOW {
err = fmt.Errorf("GetNetworkParams requested %d bytes of memory, max supported is %d. Error code is %x", ulSize, unsafe.Sizeof(fixedInfoWithOverlay{}), ret)
return
}
err = fmt.Errorf("GetNetworkParams failed with code is %x", ret)
return
}
fi := (*fixedInfoWithOverlay)(unsafe.Pointer(buf))
var p *ipAddrString = &fi.DnsServerList
for {
ip := make([]byte, ip_size)
for i := 0; i < len(p.IpAddress) && p.IpAddress[i] != 0; i++ {
ip[i] = p.IpAddress[i]
}
servers = append(servers, MakeResolverAddress(string(ip), "53"))
if p.Next == 0 {
break
}
p = (*ipAddrString)(unsafe.Pointer(p.Next))
}
timeout = DefaultTimeout
return
}
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