new GetLocalIpAddress() function

- used also to implement GetLocalMacAddress() on POSIX systems

src/mormot.commit.inc

@@ -1 +1 @@
-'2.1.6337'
+'2.1.6338'

src/net/mormot.net.sock.pas

@@ -574,13 +574,18 @@ function GetMacAddressesText(WithoutName: boolean = true;
 // on POSIX, implementing ARP sadly requires root rights
 // - return the MAC address as a 12 hexa chars ('0050C204C80A' e.g.)
 function GetRemoteMacAddress(const IP: RawUtf8): RawUtf8;
+{$endif OSWINDOWS}
 
-/// get the local MAC address used to reach a computer, from its IP Address
+/// get the local MAC address used to reach a computer, from its IP or Host name
 // - return the local interface as a TMacAddress, with all its available info
-// - only works under Windows, which features a GetBestInterface() API
-function GetLocalMacAddress(const IP: RawUtf8;
-  var Mac: TMacAddress): boolean;
-{$endif OSWINDOWS}
+// - under Windows, will call the GetBestInterface() API
+// - on POSIX, calls GetLocalIpAddress() then create and discard a SOCK_DGRAM
+function GetLocalMacAddress(const Remote: RawUtf8; var Mac: TMacAddress): boolean;
+
+/// get the local IP address used to reach a computer, from its IP Address
+// - will create a SOCK_DGRAM socket over the supplied IP, and check
+// the local socket address created
+function GetLocalIpAddress(const IP: RawUtf8): RawUtf8;
 
 /// retrieve all DNS (Domain Name Servers) addresses known by the Operating System
 // - on POSIX, return "nameserver" from /etc/resolv.conf unless usePosixEnv is set
@@ -3156,6 +3161,25 @@ function _GetSystemMacAddress: TRawUtf8DynArray;
   SetLength(result, n);
 end;
 
+function GetLocalIpAddress(const IP: RawUtf8): RawUtf8;
+var
+  addr: TNetAddr;
+  sock: TNetSocket;
+begin
+  result := '';
+  if addr.SetFrom(IP, '9', nlUdp) <> nrOk then // discard port
+    exit;
+  sock := addr.NewSocket(nlUdp);
+  if sock <> nil then
+    try
+      if (connect(sock.Socket, @addr, addr.Size) = NO_ERROR) and
+         (sock.GetName(addr) = nrOk) then
+        addr.IP(result);
+    finally
+      sock.Close;
+    end;
+end;
+
 var
   DnsCache: record
     Safe: TLightLock;

src/net/mormot.net.sock.posix.inc

@@ -920,6 +920,26 @@ end;
 
 {$endif USE_IFADDRS}
 
+function GetLocalMacAddress(const IP: RawUtf8; var Mac: TMacAddress): boolean;
+var
+  local: RawUtf8;
+  all: TMacAddressDynArray;
+  i: PtrInt;
+begin
+  result := false;
+  local := GetLocalIpAddress(IP);
+  if local = '' then
+    exit;
+  all := GetMacAddresses;
+  for i := 0 to high(all) do
+    if all[i].IP = local then
+    begin
+      mac := all[i];
+      result := true;
+      break;
+    end;
+end;
+
 function _GetDnsAddresses(usePosixEnv, getAD: boolean): TRawUtf8DynArray;
 var
   resolv, one: RawUtf8;

src/net/mormot.net.sock.windows.inc

@@ -693,6 +693,7 @@ type
 
 var
   iphlpapiDll: THandle;
+
   // some iphlpapi.dll late-binded API via DelayedProc()
   GetIpAddrTable: function (pIpAddrTable: PMIB_IPADDRTABLE;
     var pdwSize: DWORD; bOrder: BOOL): DWORD; stdcall;
@@ -736,10 +737,11 @@ const
   GAA_FLAG_SKIP_DNS_SERVER    = $8;
   GAA_FLAG_INCLUDE_PREFIX     = $10;
   GAA_FLAG_SKIP_FRIENDLY_NAME = $20;
-  // Vista+
+  // below flags are only available on Windows Vista and later
   GAA_FLAG_INCLUDE_WINS_INFO  = $40;
   GAA_FLAG_INCLUDE_GATEWAYS   = $80;
   GAA_FLAG_INCLUDE_ALL_INTERFACES = $100;
+
   IfOperStatusUp = 1;
   IfOperStatusDown = 2;
   IF_TYPE_SOFTWARE_LOOPBACK = 24;
@@ -867,18 +869,14 @@ type
   end;
   PFIXED_INFO = ^FIXED_INFO;
 
-
 var
-  // some iphlpapi.dll late-binded APIs via DelayedProc()
+  // some iphlpapi.dll late-binded API via DelayedProc()
   GetAdaptersAddresses: function(Family: ULONG; Flags: DWORD; Reserved: pointer;
-    pAdapterAddresses: PIP_ADAPTER_ADDRESSES; pOutBufLen: PULONG): DWORD; stdcall;
-
+      pAdapterAddresses: PIP_ADAPTER_ADDRESSES; pOutBufLen: PULONG): DWORD; stdcall;
   SendARP: function(DestIp: DWORD; srcIP: DWORD; pMacAddr: pointer;
     PhyAddrLen: Pointer): DWORD; stdcall;
-
   GetNetworkParams: function(pFixedInfo: PFIXED_INFO;
     pOutBufLen: PULONG): DWORD; stdcall;
-
   GetBestInterface: function(dwDestAddrIPv4: cardinal;
     var pdwBestIfIndex: DWORD): DWORD; stdcall;
 
@@ -1034,15 +1032,19 @@ begin
   until p = nil;
 end;
 
-function GetLocalMacAddress(const IP: RawUtf8;
+function GetLocalMacAddress(const Remote: RawUtf8;
   var Mac: TMacAddress): boolean;
 var
+  addr: TNetAddr;
   dwRemoteIP, ifIndex: DWORD;
   all: TMacAddressDynArray;
   i: PtrInt;
 begin
   result := false;
-  if NetIsIP4(pointer(IP), @dwRemoteIP) and
+  if not addr.SetFromIP4(Remote, {nolookup=}false) then
+    exit;
+  dwRemoteIP := addr.IP4;
+  if (dwRemoteIP <> 0) and
      DelayedProc(GetBestInterface, iphlpapiDll,
        'iphlpapi.dll', 'GetBestInterface') and
      (GetBestInterface(dwRemoteIP, ifIndex) = NO_ERROR) then