IpSecManager and IpSecTransform API Cleanup

-Remove Int-based SPI usage from the IpSecTransform.Builder
 This is essentially a less-safe method overload, and it is both
 unnecessary and difficult to implement: the cross-validation
 between SPI and Transform is actually useful, and the kernel
 requires two different mechanisms to use an unreserved vs a
 reserved (alloc'd) SPI: CREATESA vs UPDATESA, which makes this
 hard to support. API Council has questioned the value of this,
 and they are right: everything points to "remove this". In the
 future, if we find that SPI reservation is overhead, we can
 always add it back.

-Hiding the TunnelMode builder method and application/remove
 methods. These will not land by the time the next API
 stabilizes, so better to hide them now that this is a
 near-certainty. Expectation is to un-hide them in the subsequent
 API bump.

Bug: 36073210
Test: Compilation, verified nobody is calling these stubs
Change-Id: Ic1a3f2cf7128633318ac175d6b56b45eb8d21cab

core/java/android/net/IpSecManager.java

@@ -197,7 +197,6 @@ public final class IpSecManager {
      * @param transform an {@link IpSecTransform}, which must be an active Tunnel Mode transform.
      * @hide
      */
-    @SystemApi
     public void applyTunnelModeTransform(Network net, IpSecTransform transform) {}
 
     /**
@@ -242,7 +241,6 @@ public final class IpSecManager {
      *     network
      * @hide
      */
-    @SystemApi
     public void removeTunnelModeTransform(Network net, IpSecTransform transform) {}
 
     /**

core/java/android/net/IpSecTransform.java

@@ -305,32 +305,9 @@ public final class IpSecTransform implements AutoCloseable {
          * given destination address.
          *
          * <p>Care should be chosen when selecting an SPI to ensure that is is as unique as
-         * possible. Random number generation is a reasonable approach to selecting an SPI. For
+         * possible. To reserve a value call {@link IpSecManager#reserveSecurityParameterIndex(int,
-         * outbound SPIs, they must be reserved by calling {@link
+         * InetAddress, int)}. Otherwise, SPI collisions would prevent a transform from being
-         * IpSecManager#reserveSecurityParameterIndex(int, InetAddress, int)}. Otherwise, Transforms will
+         * activated. IpSecManager#reserveSecurityParameterIndex(int, InetAddres$s, int)}.
-         * fail to build.
-         *
-         * <p>Unless an SPI is set for a given direction, traffic in that direction will be
-         * sent/received without any IPsec applied.
-         *
-         * @param direction either {@link #DIRECTION_IN or #DIRECTION_OUT}
-         * @param spi a unique 32-bit integer to identify transformed traffic
-         */
-        public IpSecTransform.Builder setSpi(@TransformDirection int direction, int spi) {
-            mConfig.flow[direction].spi = spi;
-            return this;
-        }
-
-        /**
-         * Set the SPI, which uniquely identifies a particular IPsec session from others. Because
-         * IPsec operates at the IP layer, this 32-bit identifier uniquely identifies packets to a
-         * given destination address.
-         *
-         * <p>Care should be chosen when selecting an SPI to ensure that is is as unique as
-         * possible. Random number generation is a reasonable approach to selecting an SPI. For
-         * outbound SPIs, they must be reserved by calling {@link
-         * IpSecManager#reserveSecurityParameterIndex(int, InetAddress, int)}. Otherwise, Transforms will
-         * fail to activate.
          *
          * <p>Unless an SPI is set for a given direction, traffic in that direction will be
          * sent/received without any IPsec applied.
@@ -447,7 +424,6 @@ public final class IpSecTransform implements AutoCloseable {
          *     properties is invalid.
          * @hide
          */
-        @SystemApi
         public IpSecTransform buildTunnelModeTransform(
                 InetAddress localAddress, InetAddress remoteAddress) {
             //FIXME: argument validation here