Merge "Refactor RA parsing code for simplicity." (78c81d95) · Commits · e / os / android_packages_modules_NetworkStack

src/android/net/apf/ApfFilter.java

+151 −118

Original line number	Diff line number	Diff line
		@@ -57,7 +57,6 @@ import android.system.ErrnoException;
		import android.system.Os;
		import android.text.format.DateUtils;
		import android.util.Log;
		import android.util.Pair;
		import android.util.SparseArray;

		import com.android.internal.annotations.GuardedBy;
		@@ -500,6 +499,44 @@ public class ApfFilter {
		}
		}

		/**
		* Class to keep track of a section in a packet.
		*/
		private static class PacketSection {
		public enum Type {
		MATCH, // A field that should be matched (e.g., the router IP address).
		IGNORE, // An ignored field such as the checksum of the flow label. Not matched.
		LIFETIME, // A lifetime. Not matched, and generally counts toward minimum RA lifetime.
		}

		/** The type of section. */
		public final Type type;
		/** Offset into the packet at which this section begins. */
		public final int start;
		/** Length of this section. */
		public final int length;
		/** If this is a lifetime, the ICMP option that the defined it. 0 for router lifetime. */
		public final int option;
		/** If this is a lifetime, the lifetime value. */
		public final long lifetime;

		PacketSection(int start, int length, Type type, int option, long lifetime) {
		this.start = start;
		this.length = length;
		this.type = type;
		this.option = option;
		this.lifetime = lifetime;
		}

		public String toString() {
		if (type == Type.LIFETIME) {
		return String.format("%s: (%d, %d) %d %d", type, start, length, option, lifetime);
		} else {
		return String.format("%s: (%d, %d)", type, start, length);
		}
		}
		}

		// A class to hold information about an RA.
		@VisibleForTesting
		class Ra {
		@@ -534,10 +571,10 @@ public class ApfFilter {

		// Note: mPacket's position() cannot be assumed to be reset.
		private final ByteBuffer mPacket;
		// List of binary ranges that include the whole packet except the lifetimes.
		// Pairs consist of offset and length.
		private final ArrayList<Pair<Integer, Integer>> mNonLifetimes =
		new ArrayList<Pair<Integer, Integer>>();

		// List of sections in the packet.
		private final ArrayList<PacketSection> mPacketSections = new ArrayList<>();

		// Minimum lifetime in packet
		long mMinLifetime;
		// When the packet was last captured, in seconds since Unix Epoch
		@@ -649,27 +686,65 @@ public class ApfFilter {
		}

		/**
		* Add a binary range of the packet that does not include a lifetime to mNonLifetimes.
		* Assumes mPacket.position() is as far as we've parsed the packet.
		* @param lastNonLifetimeStart offset within packet of where the last binary range of
		* data not including a lifetime.
		* @param lifetimeOffset offset from mPacket.position() to the next lifetime data.
		* @param lifetimeLength length of the next lifetime data.
		* @return offset within packet of where the next binary range of data not including
		* a lifetime. This can be passed into the next invocation of this function
		* via {@code lastNonLifetimeStart}.
		* Add a packet section that should be matched, starting from the current position.
		* @param length the length of the section
		*/
		private int addNonLifetime(int lastNonLifetimeStart, int lifetimeOffset,
		int lifetimeLength) {
		lifetimeOffset += mPacket.position();
		mNonLifetimes.add(new Pair<Integer, Integer>(lastNonLifetimeStart,
		lifetimeOffset - lastNonLifetimeStart));
		return lifetimeOffset + lifetimeLength;
		private void addMatchSection(int length) {
		// Don't generate JNEBS instruction for 0 bytes as they will fail the
		// ASSERT_FORWARD_IN_PROGRAM(pc + cmp_imm - 1) check (where cmp_imm is
		// the number of bytes to compare) and immediately pass the packet.
		// The code does not attempt to generate such matches, but add a safety
		// check to prevent doing so in the presence of bugs or malformed or
		// truncated packets.
		if (length == 0) return;
		mPacketSections.add(
		new PacketSection(mPacket.position(), length, PacketSection.Type.MATCH, 0, 0));
		mPacket.position(mPacket.position() + length);
		}

		private int addNonLifetimeU32(int lastNonLifetimeStart) {
		return addNonLifetime(lastNonLifetimeStart,
		ICMP6_4_BYTE_LIFETIME_OFFSET, ICMP6_4_BYTE_LIFETIME_LEN);
		/**
		* Add a packet section that should be matched, starting from the current position.
		* @param end the offset in the packet before which the section ends
		*/
		private void addMatchUntil(int end) {
		addMatchSection(end - mPacket.position());
		}

		/**
		* Add a packet section that should be ignored, starting from the current position.
		* @param length the length of the section in bytes
		*/
		private void addIgnoreSection(int length) {
		mPacketSections.add(
		new PacketSection(mPacket.position(), length, PacketSection.Type.IGNORE, 0, 0));
		mPacket.position(mPacket.position() + length);
		}

		/**
		* Add a packet section that represents a lifetime, starting from the current position.
		* @param length the length of the section in bytes
		* @param optionType the RA option containing this lifetime, or 0 for router lifetime
		* @param lifetime the lifetime
		*/
		private void addLifetimeSection(int length, int optionType, long lifetime) {
		mPacketSections.add(
		new PacketSection(mPacket.position(), length, PacketSection.Type.LIFETIME,
		optionType, lifetime));
		mPacket.position(mPacket.position() + length);
		}

		/**
		* Adds packet sections for an RA option with a 4-byte lifetime 4 bytes into the option
		* @param optionType the RA option that is being added
		* @param optionLength the length of the option in bytes
		*/
		private long add4ByteLifetimeOption(int optionType, int optionLength) {
		addMatchSection(ICMP6_4_BYTE_LIFETIME_OFFSET);
		final long lifetime = getUint32(mPacket, mPacket.position());
		addLifetimeSection(ICMP6_4_BYTE_LIFETIME_LEN, optionType, lifetime);
		addMatchSection(optionLength - ICMP6_4_BYTE_LIFETIME_OFFSET
		- ICMP6_4_BYTE_LIFETIME_LEN);
		return lifetime;
		}

		// Note that this parses RA and may throw InvalidRaException (from
		@@ -696,20 +771,18 @@ public class ApfFilter {
		RaEvent.Builder builder = new RaEvent.Builder();

		// Ignore the flow label and low 4 bits of traffic class.
		int lastNonLifetimeStart = addNonLifetime(0,
		IPV6_FLOW_LABEL_OFFSET,
		IPV6_FLOW_LABEL_LEN);
		addMatchUntil(IPV6_FLOW_LABEL_OFFSET);
		addIgnoreSection(IPV6_FLOW_LABEL_LEN);

		// Ignore the checksum.
		lastNonLifetimeStart = addNonLifetime(lastNonLifetimeStart,
		ICMP6_RA_CHECKSUM_OFFSET,
		ICMP6_RA_CHECKSUM_LEN);
		// Ignore checksum.
		addMatchUntil(ICMP6_RA_CHECKSUM_OFFSET);
		addIgnoreSection(ICMP6_RA_CHECKSUM_LEN);

		// Parse router lifetime
		lastNonLifetimeStart = addNonLifetime(lastNonLifetimeStart,
		ICMP6_RA_ROUTER_LIFETIME_OFFSET,
		ICMP6_RA_ROUTER_LIFETIME_LEN);
		builder.updateRouterLifetime(getUint16(mPacket, ICMP6_RA_ROUTER_LIFETIME_OFFSET));
		addMatchUntil(ICMP6_RA_ROUTER_LIFETIME_OFFSET);
		final long routerLifetime = getUint16(mPacket, ICMP6_RA_ROUTER_LIFETIME_OFFSET);
		addLifetimeSection(ICMP6_RA_ROUTER_LIFETIME_LEN, 0, routerLifetime);
		builder.updateRouterLifetime(routerLifetime);

		// Ensures that the RA is not truncated.
		mPacket.position(ICMP6_RA_OPTION_OFFSET);
		@@ -720,64 +793,62 @@ public class ApfFilter {
		long lifetime;
		switch (optionType) {
		case ICMP6_PREFIX_OPTION_TYPE:
		mPrefixOptionOffsets.add(position);

		// Parse valid lifetime
		lastNonLifetimeStart = addNonLifetime(lastNonLifetimeStart,
		ICMP6_PREFIX_OPTION_VALID_LIFETIME_OFFSET,
		ICMP6_PREFIX_OPTION_VALID_LIFETIME_LEN);
		lifetime = getUint32(mPacket,
		position + ICMP6_PREFIX_OPTION_VALID_LIFETIME_OFFSET);
		addMatchSection(ICMP6_PREFIX_OPTION_VALID_LIFETIME_LEN);
		lifetime = getUint32(mPacket, mPacket.position());
		addLifetimeSection(ICMP6_PREFIX_OPTION_VALID_LIFETIME_LEN,
		ICMP6_PREFIX_OPTION_TYPE, lifetime);
		builder.updatePrefixValidLifetime(lifetime);

		// Parse preferred lifetime
		lastNonLifetimeStart = addNonLifetime(lastNonLifetimeStart,
		ICMP6_PREFIX_OPTION_PREFERRED_LIFETIME_OFFSET,
		ICMP6_PREFIX_OPTION_PREFERRED_LIFETIME_LEN);
		lifetime = getUint32(mPacket,
		position + ICMP6_PREFIX_OPTION_PREFERRED_LIFETIME_OFFSET);
		lifetime = getUint32(mPacket, mPacket.position());
		addLifetimeSection(ICMP6_PREFIX_OPTION_PREFERRED_LIFETIME_LEN,
		ICMP6_PREFIX_OPTION_TYPE, lifetime);
		builder.updatePrefixPreferredLifetime(lifetime);
		mPrefixOptionOffsets.add(position);

		addMatchSection(4); // Reserved bytes
		addMatchSection(IPV6_ADDR_LEN); // The prefix itself
		break;
		// These three options have the same lifetime offset and size, and
		// are processed with the same specialized addNonLifetimeU32:
		// are processed with the same specialized add4ByteLifetimeOption:
		case ICMP6_RDNSS_OPTION_TYPE:
		mRdnssOptionOffsets.add(position);
		lastNonLifetimeStart = addNonLifetimeU32(lastNonLifetimeStart);
		lifetime = getUint32(mPacket, position + ICMP6_4_BYTE_LIFETIME_OFFSET);
		lifetime = add4ByteLifetimeOption(optionType, optionLength);
		builder.updateRdnssLifetime(lifetime);
		break;
		case ICMP6_ROUTE_INFO_OPTION_TYPE:
		mRioOptionOffsets.add(position);
		lastNonLifetimeStart = addNonLifetimeU32(lastNonLifetimeStart);
		lifetime = getUint32(mPacket, position + ICMP6_4_BYTE_LIFETIME_OFFSET);
		lifetime = add4ByteLifetimeOption(optionType, optionLength);
		builder.updateRouteInfoLifetime(lifetime);
		break;
		case ICMP6_DNSSL_OPTION_TYPE:
		lastNonLifetimeStart = addNonLifetimeU32(lastNonLifetimeStart);
		lifetime = getUint32(mPacket, position + ICMP6_4_BYTE_LIFETIME_OFFSET);
		lifetime = add4ByteLifetimeOption(optionType, optionLength);
		builder.updateDnsslLifetime(lifetime);
		break;
		default:
		// RFC4861 section 4.2 dictates we ignore unknown options for fowards
		// RFC4861 section 4.2 dictates we ignore unknown options for forwards
		// compatibility.
		mPacket.position(position + optionLength);
		break;
		}
		if (optionLength <= 0) {
		throw new InvalidRaException(String.format(
		"Invalid option length opt=%d len=%d", optionType, optionLength));
		}
		mPacket.position(position + optionLength);
		}
		// Mark non-lifetime bytes since last lifetime.
		addNonLifetime(lastNonLifetimeStart, 0, 0);
		mMinLifetime = minLifetime(packet, length);
		mMinLifetime = minLifetime();
		mMetricsLog.log(builder.build());
		}

		// Ignoring lifetimes (which may change) does {@code packet} match this RA?
		// Considering only the MATCH sections, does {@code packet} match this RA?
		boolean matches(byte[] packet, int length) {
		if (length != mPacket.capacity()) return false;
		byte[] referencePacket = mPacket.array();
		for (Pair<Integer, Integer> nonLifetime : mNonLifetimes) {
		for (int i = nonLifetime.first; i < (nonLifetime.first + nonLifetime.second); i++) {
		for (PacketSection section : mPacketSections) {
		if (section.type != PacketSection.Type.MATCH) continue;
		for (int i = section.start; i < (section.start + section.length); i++) {
		if (packet[i] != referencePacket[i]) return false;
		}
		}
		@@ -786,36 +857,12 @@ public class ApfFilter {

		// What is the minimum of all lifetimes within {@code packet} in seconds?
		// Precondition: matches(packet, length) already returned true.
		long minLifetime(byte[] packet, int length) {
		long minLifetime() {
		long minLifetime = Long.MAX_VALUE;
		// Wrap packet in ByteBuffer so we can read big-endian values easily
		ByteBuffer byteBuffer = ByteBuffer.wrap(packet);
		for (int i = 0; (i + 1) < mNonLifetimes.size(); i++) {
		int offset = mNonLifetimes.get(i).first + mNonLifetimes.get(i).second;

		// The flow label is in mNonLifetimes, but it's not a lifetime.
		if (offset == IPV6_FLOW_LABEL_OFFSET) {
		continue;
		}

		// The checksum is in mNonLifetimes, but it's not a lifetime.
		if (offset == ICMP6_RA_CHECKSUM_OFFSET) {
		continue;
		}

		final int lifetimeLength = mNonLifetimes.get(i+1).first - offset;
		final long optionLifetime;
		switch (lifetimeLength) {
		case 2:
		optionLifetime = getUint16(byteBuffer, offset);
		break;
		case 4:
		optionLifetime = getUint32(byteBuffer, offset);
		break;
		default:
		throw new IllegalStateException("bogus lifetime size " + lifetimeLength);
		for (PacketSection section : mPacketSections) {
		if (section.type == PacketSection.Type.LIFETIME) {
		minLifetime = Math.min(minLifetime, section.lifetime);
		}
		minLifetime = Math.min(minLifetime, optionLifetime);
		}
		return minLifetime;
		}
		@@ -844,38 +891,24 @@ public class ApfFilter {
		// Skip filter if expired
		gen.addLoadFromMemory(Register.R0, gen.FILTER_AGE_MEMORY_SLOT);
		gen.addJumpIfR0GreaterThan(filterLifetime, nextFilterLabel);
		for (int i = 0; i < mNonLifetimes.size(); i++) {
		// Generate code to match the packet bytes
		Pair<Integer, Integer> nonLifetime = mNonLifetimes.get(i);
		// Don't generate JNEBS instruction for 0 bytes as it always fails the
		// ASSERT_FORWARD_IN_PROGRAM(pc + cmp_imm - 1) check where cmp_imm is
		// the number of bytes to compare. nonLifetime is zero between the
		// valid and preferred lifetimes in the prefix option.
		if (nonLifetime.second != 0) {
		gen.addLoadImmediate(Register.R0, nonLifetime.first);
		for (PacketSection section : mPacketSections) {
		// Generate code to match the packet bytes.
		if (section.type == PacketSection.Type.MATCH) {
		gen.addLoadImmediate(Register.R0, section.start);
		gen.addJumpIfBytesNotEqual(Register.R0,
		Arrays.copyOfRange(mPacket.array(), nonLifetime.first,
		nonLifetime.first + nonLifetime.second),
		Arrays.copyOfRange(mPacket.array(), section.start,
		section.start + section.length),
		nextFilterLabel);
		}
		// Generate code to test the lifetimes haven't gone down too far
		if ((i + 1) < mNonLifetimes.size()) {
		Pair<Integer, Integer> nextNonLifetime = mNonLifetimes.get(i + 1);
		int offset = nonLifetime.first + nonLifetime.second;

		// Skip the Flow label.
		if (offset == IPV6_FLOW_LABEL_OFFSET) {
		continue;
		}
		// Skip the checksum.
		if (offset == ICMP6_RA_CHECKSUM_OFFSET) {
		continue;
		}
		int length = nextNonLifetime.first - offset;
		switch (length) {
		case 4: gen.addLoad32(Register.R0, offset); break;
		case 2: gen.addLoad16(Register.R0, offset); break;
		default: throw new IllegalStateException("bogus lifetime size " + length);
		// Generate code to test the lifetimes haven't gone down too far.
		// The packet is accepted if any of its lifetimes are lower than filterLifetime.
		if (section.type == PacketSection.Type.LIFETIME) {
		switch (section.length) {
		case 4: gen.addLoad32(Register.R0, section.start); break;
		case 2: gen.addLoad16(Register.R0, section.start); break;
		default:
		throw new IllegalStateException(
		"bogus lifetime size " + section.length);
		}
		gen.addJumpIfR0LessThan(filterLifetime, nextFilterLabel);
		}
		@@ -1682,7 +1715,7 @@ public class ApfFilter {
		if (VDBG) log("matched RA " + ra);
		// Update lifetimes.
		ra.mLastSeen = currentTimeSeconds();
		ra.mMinLifetime = ra.minLifetime(packet, length);
		ra.mMinLifetime = ra.minLifetime();
		ra.seenCount++;

		// Keep mRas in LRU order so as to prioritize generating filters for recently seen