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ebtables-segment-mld: Segment IGMP/MLD domain

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This patch adds a new gluon-ebtables package to filter IGMP/MLD messages
via ebtables.

For one thing this reduces multicast overhead: About one third of all
ICMPv6 multicast traffic in Lübeck or Hamburg is MLD.

Furthermore it removes a potential Distributed Denial-of-Service vector
(see Gluon ticket #553).

Finally, it is a prerequisite for enabling bridge multicast snooping in
a decentral and robust fashion.

Note that IGMP/MLD are filtered for multicast traffic coming from
the mesh, too (new MULTICAST_IN), as unfortunately there seem to
be other queriers somewhere in the mesh at least for Freifunk
Lübeck. Also adding these rules to be prepared to anyone intentionally
or unintentionally disabling these filters on his/her node.

Node operators not running Gluon (for instance gateway nodes) should
make sure to either enable multicast_router towards bat0 or disable
multicast snooping entirely if they have a bridge on top of bat0.

Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
This commit is contained in:
Linus Lüssing 2016-03-08 08:10:20 +01:00
parent 8e891b2cc4
commit 4199b216c6
13 changed files with 102 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
docs/package/gluon-ebtables-segment-mld.rst Normal file
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@ -0,0 +1,16 @@
gluon-ebtables-segment-mld
==========================
These filters drop IGMP/MLD packets before they enter the mesh and
filter any IGMP/MLD packets coming from the mesh.
IGMP/MLD have the concept of a local, elected Querier. For more
decentralization and increased robustness, the idea of this package is
to split the IGMP/MLD domain a querier is responsible for, allowing to
have a querier per node. The split IGMP/MLD domain will also reduce
overhead for this packet type, increasing scalability.
Beware of the consequences of using this package though: You might need
to explicitly, manually mark ports on snooping switches leading towards
your mesh node as multicast router ports for now (Multicast Router
Discovery, MRD, not implemented yet).

1
package/gluon-ebtables-filter-multicast/files/lib/gluon/ebtables/100-mcast-chain
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@ -1 +0,0 @@
chain('MULTICAST_OUT', 'DROP')

6
package/gluon-ebtables-filter-multicast/files/lib/gluon/ebtables/110-mcast-allow-icmpv6
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@ -1,3 +1,3 @@
rule 'MULTICAST_OUT -p IPv6 --ip6-protocol ipv6-icmp --ip6-icmp-type echo-request -j DROP'
rule 'MULTICAST_OUT -p IPv6 --ip6-protocol ipv6-icmp --ip6-icmp-type 139 -j DROP'
rule 'MULTICAST_OUT -p IPv6 --ip6-protocol ipv6-icmp -j RETURN'
rule 'MULTICAST_OUT_ICMPV6 -p IPv6 --ip6-protocol ipv6-icmp --ip6-icmp-type echo-request -j RETURN'
rule 'MULTICAST_OUT_ICMPV6 -p IPv6 --ip6-protocol ipv6-icmp --ip6-icmp-type 139 -j RETURN' -- ICMP Node Information Query
rule 'MULTICAST_OUT_ICMPV6 -j ACCEPT'

2
package/gluon-ebtables-filter-multicast/files/lib/gluon/ebtables/300-mcast
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@ -1,2 +0,0 @@
rule 'FORWARD --logical-out br-client -o bat0 -d Multicast -j MULTICAST_OUT'
rule 'OUTPUT --logical-out br-client -o bat0 -d Multicast -j MULTICAST_OUT'

1
package/gluon-ebtables-filter-multicast/files/lib/gluon/ebtables/355-mcast-drop Normal file
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@ -0,0 +1 @@
rule ('MULTICAST_OUT -j DROP')

51
package/gluon-ebtables-segment-mld/Makefile Normal file
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@ -0,0 +1,51 @@
include $(TOPDIR)/rules.mk
PKG_NAME:=gluon-ebtables-segment-mld
PKG_VERSION:=1
PKG_RELEASE:=1
PKG_BUILD_DIR := $(BUILD_DIR)/$(PKG_NAME)
include $(INCLUDE_DIR)/package.mk
define Package/gluon-ebtables-segment-mld
SECTION:=gluon
CATEGORY:=Gluon
TITLE:=Ebtables filters for IGMP/MLD packets
DEPENDS:=+gluon-core +gluon-ebtables
endef
define Package/gluon-ebtables-segment-mld/description
Gluon community wifi mesh firmware framework: Ebtables filters for
IGMP/MLD packets
These filters drop IGMP/MLD packets before they enter the mesh and
filter any IGMP/MLD packets coming from the mesh.
IGMP/MLD have the concept of a local, elected Querier. For more
decentralization and increased robustness, the idea of this package is
to split the IGMP/MLD domain a querier is responsible for, allowing to
have a querier per node. The split IGMP/MLD domain will also reduce
overhead for this packet type, increasing scalability.
Beware of the consequences of using this package though: You might need
to explicitly, manually mark ports on snooping switches leading towards
your mesh node as multicast router ports for now (Multicast Router
Discovery, MRD, not implemented yet).
endef
define Build/Prepare
mkdir -p $(PKG_BUILD_DIR)
endef
define Build/Configure
endef
define Build/Compile
endef
define Package/gluon-ebtables-segment-mld/install
$(CP) ./files/* $(1)/
endef
$(eval $(call BuildPackage,gluon-ebtables-segment-mld))

2
package/gluon-ebtables-segment-mld/files/lib/gluon/ebtables/100-mcast-in-chain Normal file
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@ -0,0 +1,2 @@
chain('MULTICAST_IN', 'RETURN', 'nat')
chain('MULTICAST_IN_ICMPV6', 'RETURN', 'nat')

2
package/gluon-ebtables-segment-mld/files/lib/gluon/ebtables/101-mcast-in-rule Normal file
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@ -0,0 +1,2 @@
rule ('PREROUTING -d Multicast --logical-in br-client -i bat0 -j MULTICAST_IN', 'nat')
rule ('MULTICAST_IN -p IPv6 --ip6-protocol ipv6-icmp -j MULTICAST_IN_ICMPV6', 'nat')

2
package/gluon-ebtables-segment-mld/files/lib/gluon/ebtables/105-mcast-drop-igmp Normal file
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@ -0,0 +1,2 @@
rule('MULTICAST_OUT -p IPv4 --ip-protocol igmp -j DROP')
rule('MULTICAST_IN -p IPv4 --ip-protocol igmp -j DROP', 'nat')

9
package/gluon-ebtables-segment-mld/files/lib/gluon/ebtables/105-mcast-drop-mld Normal file
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@ -0,0 +1,9 @@
rule('MULTICAST_OUT_ICMPV6 -p IPv6 --ip6-protocol ipv6-icmp --ip6-icmp-type 130 -j DROP') -- MLD Query
rule('MULTICAST_OUT_ICMPV6 -p IPv6 --ip6-protocol ipv6-icmp --ip6-icmp-type 131 -j DROP') -- MLDv1 Report
rule('MULTICAST_OUT_ICMPV6 -p IPv6 --ip6-protocol ipv6-icmp --ip6-icmp-type 132 -j DROP') -- MLDv1 Done
rule('MULTICAST_OUT_ICMPV6 -p IPv6 --ip6-protocol ipv6-icmp --ip6-icmp-type 143 -j DROP') -- MLDv2 Report
rule('MULTICAST_IN_ICMPV6 -p IPv6 --ip6-protocol ipv6-icmp --ip6-icmp-type 130 -j DROP', 'nat') -- MLD Query
rule('MULTICAST_IN_ICMPV6 -p IPv6 --ip6-protocol ipv6-icmp --ip6-icmp-type 131 -j DROP', 'nat') -- MLDv1 Report
rule('MULTICAST_IN_ICMPV6 -p IPv6 --ip6-protocol ipv6-icmp --ip6-icmp-type 132 -j DROP', 'nat') -- MLDv1 Done
rule('MULTICAST_IN_ICMPV6 -p IPv6 --ip6-protocol ipv6-icmp --ip6-icmp-type 143 -j DROP', 'nat') -- MLDv2 Report

15
package/gluon-ebtables/files/etc/init.d/gluon-ebtables
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@ -24,12 +24,15 @@ exec_file() {
local file="$1"
/usr/bin/lua -e "
function rule(command)
function rule(command, table)
table = table or 'filter'
os.execute($EBTABLES_RULE)
end
function chain(name, policy)
function chain(name, policy, table)
table = table or 'filter'
os.execute($EBTABLES_CHAIN)
end
" "$file"
}
@ -48,8 +51,8 @@ exec_all() {
start() {
(
export EBTABLES_RULE='"ebtables -A " .. command'
export EBTABLES_CHAIN='"ebtables -N " .. name .. " -P " .. policy'
export EBTABLES_RULE='"ebtables -t " .. table .. " -A " .. command'
export EBTABLES_CHAIN='"ebtables -t " .. table .. " -N " .. name .. " -P " .. policy'
if [ -z "$1" ]; then
exec_all ''
@ -61,8 +64,8 @@ start() {
stop() {
(
export EBTABLES_RULE='"ebtables -D " .. command'
export EBTABLES_CHAIN='"ebtables -X " .. name'
export EBTABLES_RULE='"ebtables -t " .. table .. " -D " .. command'
export EBTABLES_CHAIN='"ebtables -t " .. table .. " -X " .. name'
if [ -z "$1" ]; then
exec_all '-r'

3
package/gluon-ebtables/files/lib/gluon/ebtables/100-dir-chain
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@ -1,2 +1,5 @@
chain('IN_ONLY', 'RETURN')
chain('OUT_ONLY', 'RETURN')
chain('MULTICAST_OUT', 'RETURN')
chain('MULTICAST_OUT_ICMPV6', 'RETURN')

4
package/gluon-ebtables/files/lib/gluon/ebtables/350-mcast-dir-rules Normal file
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@ -0,0 +1,4 @@
rule 'OUTPUT -d Multicast --logical-out br-client -o bat0 -j MULTICAST_OUT'
rule 'FORWARD -d Multicast --logical-out br-client -o bat0 -j MULTICAST_OUT'
rule 'MULTICAST_OUT -p IPv6 --ip6-protocol ipv6-icmp -j MULTICAST_OUT_ICMPV6'