[release/6.0-maui] [Android] Fix accessing network interfaces informa…

…tion (#63628)

* [Android] Fix accessing network interfaces information (#62780)

* Re-enable tests

* Dynamically load getifaddrs if necessary

* Prevent redeclaration of the ifaddrs struct

* Fix typo

* Do not close the dynamic library

* Enable the fixed functional tests in CI

* Reduce code duplication for obtaining libc file name

* Simplify usage of the function pointers

* Move typedefs

* Rename the _ensure_ function

* Remove fptr typedefs

* Update comment

* Add missing include

* Update comment

* Remove unnecessary comment

* Move static variable

* Remove unnecessary change

* Move LIBC_FILENAME to the utilities header

* Avoid error if constant is undefined

* Conditionally include ifaddrs

* Try to fix cmake_symbol_exists issue for browser

* Minor tweaks

* Try different way of detecting getifaddrs

* Use the hack only for Android builds

* Revert "Move LIBC_FILENAME to the utilities header"

This reverts commit 4e67687.

* Revert "Reduce code duplication for obtaining libc file name"

This reverts commit aca15d1.

* Simplify opening libc

* Update code style

* Fix race condition

* Prevent race condition

* Switch locking implementation for a lock-free implementation

* Enable unit test for Android

* Try using weak symbols

* Fix function name

* Revert "Fix function name"

This reverts commit f927aae.

* Revert "Try using weak symbols"

This reverts commit 46d3ede.

* Refactor code to use pthread_once

* [Android] Throw PNSE for unavailable network information (#63633)

* Update tests

* Add android specific implementation

* Add UnsupportedOSPlatform attributes

* Fix typo

* Remove unnecessary file reference

* Clean-up code

* Minor code clean-up

* Remove dictionary

* Refactoring

* Revert comment change

* Fix usage of Interop.Sys.GetNetworkInterfaces

src/libraries/Native/Unix/Common/pal_config.h.in

@@ -12,6 +12,7 @@
 #cmakedefine01 HAVE_F_FULLFSYNC
 #cmakedefine01 HAVE_O_CLOEXEC
 #cmakedefine01 HAVE_GETIFADDRS
+#cmakedefine01 HAVE_IFADDRS
 #cmakedefine01 HAVE_UTSNAME_DOMAINNAME
 #cmakedefine01 HAVE_STAT64
 #cmakedefine01 HAVE_FORK

src/libraries/Native/Unix/System.Native/pal_interfaceaddresses.c

@@ -11,7 +11,13 @@
 #include <stdlib.h>
 #include <sys/types.h>
 #include <assert.h>
+#if HAVE_IFADDRS || HAVE_GETIFADDRS
 #include <ifaddrs.h>
+#endif
+#if !HAVE_GETIFADDRS && TARGET_ANDROID
+#include <dlfcn.h>
+#include <pthread.h>
+#endif
 #include <net/if.h>
 #include <netinet/in.h>
 #include <string.h>
@@ -55,7 +61,6 @@
 #endif
 #endif
 
-#if HAVE_GETIFADDRS
 // Convert mask to prefix length e.g. 255.255.255.0 -> 24
 // mask parameter is pointer to buffer where address starts and length is
 // buffer length e.g. 4 for IPv4 and 16 for IPv6.
@@ -95,14 +100,67 @@ static inline uint8_t mask2prefix(uint8_t* mask, int length)
 
     return len;
 }
+
+#if !HAVE_IFADDRS && TARGET_ANDROID
+// This structure is exactly the same as struct ifaddrs defined in ifaddrs.h but since the header
+// might not be available (e.g., in bionics used in Android before API 24) we need to mirror it here
+// so that we can dynamically load the getifaddrs function and use it.
+struct ifaddrs
+{
+	struct ifaddrs *ifa_next;
+	char *ifa_name;
+	unsigned int ifa_flags;
+	struct sockaddr *ifa_addr;
+	struct sockaddr *ifa_netmask;
+	union
+	{
+		struct sockaddr *ifu_broadaddr;
+		struct sockaddr *ifu_dstaddr;
+	} ifa_ifu;
+	void *ifa_data;
+};
+#endif
+
+#if !HAVE_GETIFADDRS && TARGET_ANDROID
+// Try to load the getifaddrs and freeifaddrs functions manually.
+// This workaround is necessary on Android prior to API 24 and it can be removed once
+// we drop support for earlier Android versions.
+static int (*getifaddrs)(struct ifaddrs**) = NULL;
+static void (*freeifaddrs)(struct ifaddrs*) = NULL;
+
+static void try_loading_getifaddrs()
+{
+    void *libc = dlopen("libc.so", RTLD_NOW);
+    if (libc)
+    {
+        getifaddrs = (int (*)(struct ifaddrs**)) dlsym(libc, "getifaddrs");
+        freeifaddrs = (void (*)(struct ifaddrs*)) dlsym(libc, "freeifaddrs");
+    }
+}
+
+static bool ensure_getifaddrs_is_loaded()
+{
+    static pthread_once_t getifaddrs_is_loaded = PTHREAD_ONCE_INIT;
+    pthread_once(&getifaddrs_is_loaded, try_loading_getifaddrs);
+    return getifaddrs != NULL && freeifaddrs != NULL;
+}
 #endif
 
 int32_t SystemNative_EnumerateInterfaceAddresses(void* context,
                                                IPv4AddressFound onIpv4Found,
                                                IPv6AddressFound onIpv6Found,
                                                LinkLayerAddressFound onLinkLayerFound)
 {
-#if HAVE_GETIFADDRS
+#if !HAVE_GETIFADDRS && TARGET_ANDROID
+    // Workaround for Android API < 24
+    if (!ensure_getifaddrs_is_loaded())
+    {
+        errno = ENOTSUP;
+        return -1;
+    }
+#endif
+
+#if HAVE_GETIFADDRS || TARGET_ANDROID
     struct ifaddrs* headAddr;
     if (getifaddrs(&headAddr) == -1)
     {
@@ -235,7 +293,7 @@ int32_t SystemNative_EnumerateInterfaceAddresses(void* context,
     freeifaddrs(headAddr);
     return 0;
 #else
-    // Not supported on e.g. Android. Also, prevent a compiler error because parameters are unused
+    // Not supported. Also, prevent a compiler error because parameters are unused
     (void)context;
     (void)onIpv4Found;
     (void)onIpv6Found;
@@ -247,7 +305,16 @@ int32_t SystemNative_EnumerateInterfaceAddresses(void* context,
 
 int32_t SystemNative_GetNetworkInterfaces(int32_t * interfaceCount, NetworkInterfaceInfo **interfaceList, int32_t * addressCount, IpAddressInfo **addressList )
 {
-#if HAVE_GETIFADDRS
+#if !HAVE_GETIFADDRS && TARGET_ANDROID
+    // Workaround for Android API < 24
+    if (!ensure_getifaddrs_is_loaded())
+    {
+        errno = ENOTSUP;
+        return -1;
+    }
+#endif
+
+#if HAVE_GETIFADDRS || TARGET_ANDROID
     struct ifaddrs* head;   // Pointer to block allocated by getifaddrs().
     struct ifaddrs* ifaddrsEntry;
     IpAddressInfo *ai;
@@ -453,7 +520,7 @@ int32_t SystemNative_GetNetworkInterfaces(int32_t * interfaceCount, NetworkInter
 
     return 0;
 #else
-    // Not supported on e.g. Android. Also, prevent a compiler error because parameters are unused
+    // Not supported. Also, prevent a compiler error because parameters are unused
     (void)interfaceCount;
     (void)interfaceList;
     (void)addressCount;

src/libraries/Native/Unix/configure.cmake

@@ -7,6 +7,7 @@ include(CheckStructHasMember)
 include(CheckSymbolExists)
 include(CheckTypeSize)
 include(CheckLibraryExists)
+include(CheckFunctionExists)
 
 # CMP0075 Include file check macros honor CMAKE_REQUIRED_LIBRARIES.
 if(POLICY CMP0075)
@@ -141,6 +142,18 @@ check_c_source_compiles(
     "
     HAVE_FLOCK64)
 
+check_c_source_compiles(
+    "
+    #include <sys/types.h>
+    #include <ifaddrs.h>
+    int main(void)
+    {
+        struct ifaddrs ia;
+        return 0;
+    }
+    "
+    HAVE_IFADDRS)
+
 check_symbol_exists(
     O_CLOEXEC
     fcntl.h
@@ -156,9 +169,8 @@ check_symbol_exists(
     fcntl.h
     HAVE_F_FULLFSYNC)
 
-check_symbol_exists(
+check_function_exists(
     getifaddrs
-    ifaddrs.h
     HAVE_GETIFADDRS)
 
 check_symbol_exists(

src/libraries/System.Net.NetworkInformation/ref/System.Net.NetworkInformation.cs

@@ -123,9 +123,11 @@ public virtual void CopyTo(System.Net.NetworkInformation.IPAddressInformation[]
     public abstract partial class IPGlobalProperties
     {
         protected IPGlobalProperties() { }
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract string DhcpScopeName { get; }
         public abstract string DomainName { get; }
         public abstract string HostName { get; }
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract bool IsWinsProxy { get; }
         public abstract System.Net.NetworkInformation.NetBiosNodeType NodeType { get; }
         public virtual System.IAsyncResult BeginGetUnicastAddresses(System.AsyncCallback? callback, object? state) { throw null; }
@@ -136,58 +138,92 @@ protected IPGlobalProperties() { }
         public abstract System.Net.IPEndPoint[] GetActiveTcpListeners();
         [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract System.Net.IPEndPoint[] GetActiveUdpListeners();
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract System.Net.NetworkInformation.IcmpV4Statistics GetIcmpV4Statistics();
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract System.Net.NetworkInformation.IcmpV6Statistics GetIcmpV6Statistics();
         [System.Runtime.Versioning.UnsupportedOSPlatform("illumos")]
         [System.Runtime.Versioning.UnsupportedOSPlatform("solaris")]
         public static System.Net.NetworkInformation.IPGlobalProperties GetIPGlobalProperties() { throw null; }
         public abstract System.Net.NetworkInformation.IPGlobalStatistics GetIPv4GlobalStatistics();
         public abstract System.Net.NetworkInformation.IPGlobalStatistics GetIPv6GlobalStatistics();
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract System.Net.NetworkInformation.TcpStatistics GetTcpIPv4Statistics();
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract System.Net.NetworkInformation.TcpStatistics GetTcpIPv6Statistics();
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract System.Net.NetworkInformation.UdpStatistics GetUdpIPv4Statistics();
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract System.Net.NetworkInformation.UdpStatistics GetUdpIPv6Statistics();
         public virtual System.Net.NetworkInformation.UnicastIPAddressInformationCollection GetUnicastAddresses() { throw null; }
         public virtual System.Threading.Tasks.Task<System.Net.NetworkInformation.UnicastIPAddressInformationCollection> GetUnicastAddressesAsync() { throw null; }
     }
     public abstract partial class IPGlobalStatistics
     {
         protected IPGlobalStatistics() { }
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract int DefaultTtl { get; }
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract bool ForwardingEnabled { get; }
         public abstract int NumberOfInterfaces { get; }
         public abstract int NumberOfIPAddresses { get; }
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract int NumberOfRoutes { get; }
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract long OutputPacketRequests { get; }
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract long OutputPacketRoutingDiscards { get; }
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract long OutputPacketsDiscarded { get; }
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract long OutputPacketsWithNoRoute { get; }
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract long PacketFragmentFailures { get; }
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract long PacketReassembliesRequired { get; }
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract long PacketReassemblyFailures { get; }
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract long PacketReassemblyTimeout { get; }
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract long PacketsFragmented { get; }
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract long PacketsReassembled { get; }
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract long ReceivedPackets { get; }
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract long ReceivedPacketsDelivered { get; }
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract long ReceivedPacketsDiscarded { get; }
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract long ReceivedPacketsForwarded { get; }
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract long ReceivedPacketsWithAddressErrors { get; }
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract long ReceivedPacketsWithHeadersErrors { get; }
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract long ReceivedPacketsWithUnknownProtocol { get; }
     }
     public abstract partial class IPInterfaceProperties
     {
         protected IPInterfaceProperties() { }
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract System.Net.NetworkInformation.IPAddressInformationCollection AnycastAddresses { get; }
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract System.Net.NetworkInformation.IPAddressCollection DhcpServerAddresses { get; }
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract System.Net.NetworkInformation.IPAddressCollection DnsAddresses { get; }
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract string DnsSuffix { get; }
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract System.Net.NetworkInformation.GatewayIPAddressInformationCollection GatewayAddresses { get; }
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract bool IsDnsEnabled { get; }
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract bool IsDynamicDnsEnabled { get; }
         public abstract System.Net.NetworkInformation.MulticastIPAddressInformationCollection MulticastAddresses { get; }
         public abstract System.Net.NetworkInformation.UnicastIPAddressInformationCollection UnicastAddresses { get; }
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract System.Net.NetworkInformation.IPAddressCollection WinsServersAddresses { get; }
         public abstract System.Net.NetworkInformation.IPv4InterfaceProperties GetIPv4Properties();
         public abstract System.Net.NetworkInformation.IPv6InterfaceProperties GetIPv6Properties();
@@ -212,11 +248,16 @@ public abstract partial class IPv4InterfaceProperties
     {
         protected IPv4InterfaceProperties() { }
         public abstract int Index { get; }
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract bool IsAutomaticPrivateAddressingActive { get; }
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract bool IsAutomaticPrivateAddressingEnabled { get; }
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract bool IsDhcpEnabled { get; }
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract bool IsForwardingEnabled { get; }
         public abstract int Mtu { get; }
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public abstract bool UsesWins { get; }
     }
     public abstract partial class IPv4InterfaceStatistics
@@ -316,7 +357,9 @@ protected NetworkInterface() { }
         [System.Runtime.Versioning.UnsupportedOSPlatform("solaris")]
         public static System.Net.NetworkInformation.NetworkInterface[] GetAllNetworkInterfaces() { throw null; }
         public virtual System.Net.NetworkInformation.IPInterfaceProperties GetIPProperties() { throw null; }
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public virtual System.Net.NetworkInformation.IPInterfaceStatistics GetIPStatistics() { throw null; }
+        [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
         public virtual System.Net.NetworkInformation.IPv4InterfaceStatistics GetIPv4Statistics() { throw null; }
         [System.Runtime.Versioning.UnsupportedOSPlatform("illumos")]
         [System.Runtime.Versioning.UnsupportedOSPlatform("solaris")]

src/libraries/System.Net.NetworkInformation/src/System.Net.NetworkInformation.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Linux;$(NetCoreAppCurrent)-OSX;$(NetCoreAppCurrent)-iOS;$(NetCoreAppCurrent)-tvOS;$(NetCoreAppCurrent)-FreeBSD;$(NetCoreAppCurrent)-illumos;$(NetCoreAppCurrent)-Solaris;$(NetCoreAppCurrent)</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Linux;$(NetCoreAppCurrent)-Android;$(NetCoreAppCurrent)-OSX;$(NetCoreAppCurrent)-iOS;$(NetCoreAppCurrent)-tvOS;$(NetCoreAppCurrent)-FreeBSD;$(NetCoreAppCurrent)-illumos;$(NetCoreAppCurrent)-Solaris;$(NetCoreAppCurrent)</TargetFrameworks>
     <Nullable>enable</Nullable>
   </PropertyGroup>
   <PropertyGroup>
@@ -118,8 +118,8 @@
     <Compile Include="$(CommonPath)Interop\Unix\Interop.Errors.cs" Link="Common\Interop\CoreLib\Unix\Interop.Errors.cs" />
     <Compile Include="$(CommonPath)System\IO\RowConfigReader.cs" Link="Common\System\IO\RowConfigReader.cs" />
   </ItemGroup>
-  <!-- Linux -->
-  <ItemGroup Condition="'$(TargetsLinux)' == 'true'">
+  <!-- Linux (other than Android) -->
+  <ItemGroup Condition="'$(TargetsLinux)' == 'true' and '$(TargetsAndroid)' != 'true'">
     <Compile Include="System\Net\NetworkInformation\ExceptionHelper.Linux.cs" />
     <Compile Include="System\Net\NetworkInformation\LinuxIcmpV4Statistics.cs" />
     <Compile Include="System\Net\NetworkInformation\LinuxIcmpV6Statistics.cs" />
@@ -144,6 +144,17 @@
     <Compile Include="$(CommonPath)System\IO\StringParser.cs" Link="Common\System\IO\StringParser.cs" />
     <Compile Include="$(CommonPath)Interop\Linux\Interop.LinuxNetDeviceFlags.cs" Link="Common\Interop\Linux\Interop.LinuxNetDeviceFlags.cs" />
   </ItemGroup>
+  <!-- Android -->
+  <ItemGroup Condition="'$(TargetsAndroid)' == 'true'">
+    <Compile Include="System\Net\NetworkInformation\IPGlobalPropertiesPal.Android.cs" />
+    <Compile Include="System\Net\NetworkInformation\AndroidIPGlobalProperties.cs" />
+    <Compile Include="System\Net\NetworkInformation\AndroidIPGlobalStatistics.cs" />
+    <Compile Include="System\Net\NetworkInformation\AndroidIPInterfaceProperties.cs" />
+    <Compile Include="System\Net\NetworkInformation\AndroidIPv4InterfaceProperties.cs" />
+    <Compile Include="System\Net\NetworkInformation\AndroidIPv6InterfaceProperties.cs" />
+    <Compile Include="System\Net\NetworkInformation\NetworkInterfacePal.Android.cs" />
+    <Compile Include="System\Net\NetworkInformation\AndroidNetworkInterface.cs" />
+  </ItemGroup>
   <!-- OSX -->
   <ItemGroup Condition="'$(TargetsOSX)' == 'true' or '$(TargetsiOS)' == 'true' or '$(TargetstvOS)' == 'true' or '$(TargetsFreeBSD)' == 'true'">
     <Compile Include="System\Net\NetworkInformation\IPGlobalPropertiesPal.Bsd.cs" />

src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/AndroidIPGlobalProperties.cs

@@ -0,0 +1,32 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace System.Net.NetworkInformation
+{
+    internal sealed class AndroidIPGlobalProperties : UnixIPGlobalProperties
+    {
+        public override TcpConnectionInformation[] GetActiveTcpConnections() => throw new PlatformNotSupportedException();
+
+        public override IPEndPoint[] GetActiveTcpListeners() => throw new PlatformNotSupportedException();
+
+        public override IPEndPoint[] GetActiveUdpListeners() => throw new PlatformNotSupportedException();
+
+        public override IcmpV4Statistics GetIcmpV4Statistics() => throw new PlatformNotSupportedException();
+
+        public override IcmpV6Statistics GetIcmpV6Statistics() => throw new PlatformNotSupportedException();
+
+        public override IPGlobalStatistics GetIPv4GlobalStatistics()
+            => new AndroidIPGlobalStatistics(ipv4: true);
+
+        public override IPGlobalStatistics GetIPv6GlobalStatistics()
+            => new AndroidIPGlobalStatistics(ipv4: false);
+
+        public override TcpStatistics GetTcpIPv4Statistics() => throw new PlatformNotSupportedException();
+
+        public override TcpStatistics GetTcpIPv6Statistics() => throw new PlatformNotSupportedException();
+
+        public override UdpStatistics GetUdpIPv4Statistics() => throw new PlatformNotSupportedException();
+
+        public override UdpStatistics GetUdpIPv6Statistics() => throw new PlatformNotSupportedException();
+    }
+}