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Use APF program to drop non-IP non-ARP broadcasts

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This used to be done by some WiFi firmwares but should now be done by APF
for consistency across the board.

Bug: 28304368
Change-Id: Ic75f408affc1f56e1ecf4d347d0c287aa72250bf
This commit is contained in:
Paul Jensen
2016-05-06 10:27:56 -04:00
parent 13532bdd2e
commit dd7bee8772
1 changed files with 33 additions and 25 deletions
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58
services/net/java/android/net/apf/ApfFilter.java
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@@ -561,18 +561,21 @@ public class ApfFilter {
private void generateArpFilterLocked(ApfGenerator gen) throws IllegalInstructionException {
// Here's a basic summary of what the ARP filter program does:
//
// if it's not an ARP IPv4 request:
// pass
// if it's not a request for our IPv4 address:
// drop
// if interface has IPv4 address:
// if it's not an ARP IPv4 request:
// pass
// if it's not a request for our IPv4 address:
// drop
// pass
// if it's not an ARP IPv4 request, pass
gen.addLoadImmediate(Register.R0, ARP_HEADER_OFFSET);
gen.addJumpIfBytesNotEqual(Register.R0, ARP_IPV4_REQUEST_HEADER, gen.PASS_LABEL);
// if it's not a request for our IPv4 address, drop
gen.addLoadImmediate(Register.R0, ARP_TARGET_IP_ADDRESS_OFFSET);
gen.addJumpIfBytesNotEqual(Register.R0, mIPv4Address, gen.DROP_LABEL);
if (mIPv4Address != null) {
// if it's not an ARP IPv4 request, pass
gen.addLoadImmediate(Register.R0, ARP_HEADER_OFFSET);
gen.addJumpIfBytesNotEqual(Register.R0, ARP_IPV4_REQUEST_HEADER, gen.PASS_LABEL);
// if it's not a request for our IPv4 address, drop
gen.addLoadImmediate(Register.R0, ARP_TARGET_IP_ADDRESS_OFFSET);
gen.addJumpIfBytesNotEqual(Register.R0, mIPv4Address, gen.DROP_LABEL);
}
// Otherwise, pass
gen.addJump(gen.PASS_LABEL);
@@ -668,6 +671,7 @@ public class ApfFilter {
* <li>Drop IPv4 broadcast packets, except DHCP destined to our MAC,
* <li>Drop IPv4 multicast packets, if mMulticastFilter,
* <li>Pass all other IPv4 packets,
* <li>Drop all broadcast non-IP non-ARP packets.
* <li>Pass all non-ICMPv6 IPv6 packets,
* <li>Pass all non-IPv4 and non-IPv6 packets,
* <li>Drop IPv6 ICMPv6 NAs to ff02::1.
@@ -684,24 +688,21 @@ public class ApfFilter {
// Here's a basic summary of what the initial program does:
//
// if it's ARP:
// inesrt ARP filter to drop or pass these appropriately
// insert ARP filter to drop or pass these appropriately
// if it's IPv4:
// insert IPv4 filter to drop or pass these appropriately
// if it's not IPv6:
// if it's broadcast:
// drop
// pass
// insert IPv6 filter to drop, pass, or fall off the end for ICMPv6 packets
// Add ARP filters:
String skipArpFiltersLabel = "skipArpFilters";
gen.addLoad16(Register.R0, ETH_ETHERTYPE_OFFSET);
if (mIPv4Address != null) {
// Add ARP filters:
String skipArpFiltersLabel = "skipArpFilters";
// If not ARP, skip ARP filters
// NOTE: Relies on R0 containing ethertype.
gen.addJumpIfR0NotEquals(ETH_P_ARP, skipArpFiltersLabel);
generateArpFilterLocked(gen);
gen.defineLabel(skipArpFiltersLabel);
}
gen.addJumpIfR0NotEquals(ETH_P_ARP, skipArpFiltersLabel);
generateArpFilterLocked(gen);
gen.defineLabel(skipArpFiltersLabel);
// Add IPv4 filters:
String skipIPv4FiltersLabel = "skipIPv4Filters";
@@ -709,16 +710,23 @@ public class ApfFilter {
// execute the ARP filter, since that filter does not fall through, but either drops or
// passes.
gen.addJumpIfR0NotEquals(ETH_P_IP, skipIPv4FiltersLabel);
// NOTE: Relies on R1 being initialized to 0.
generateIPv4FilterLocked(gen);
gen.defineLabel(skipIPv4FiltersLabel);
// Add IPv6 filters:
// If not IPv6, pass
// Check for IPv6:
// NOTE: Relies on R0 containing ethertype. This is safe because if we got here, we did not
// execute the ARP or IPv4 filters, since those filters do not fall through, but either
// drop or pass.
gen.addJumpIfR0NotEquals(ETH_P_IPV6, gen.PASS_LABEL);
String ipv6FilterLabel = "IPv6Filters";
gen.addJumpIfR0Equals(ETH_P_IPV6, ipv6FilterLabel);
// Drop non-IP non-ARP broadcasts, pass the rest
gen.addLoadImmediate(Register.R0, ETH_DEST_ADDR_OFFSET);
gen.addJumpIfBytesNotEqual(Register.R0, ETH_BROADCAST_MAC_ADDRESS, gen.PASS_LABEL);
gen.addJump(gen.DROP_LABEL);
// Add IPv6 filters:
gen.defineLabel(ipv6FilterLabel);
generateIPv6FilterLocked(gen);
return gen;
}