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- Linux Driver for Keystone NetCP Ethernet Network Connection
- ===========================================================
- Keystone netcp driver files are located at drivers/net/ethernet/ti/netcp*
- sysfs entry to configure special packet handling
- ================================================
- mcast_filter
- ------------
- This is a hack solution to implement special packet processing
- for specific marked packets. The intended use is:
- 1. Ethernet interfaces are part of a bridge
- 2. The switch is enabled (by default it is not) through sysfs command
- 3. ALE is enabled through sysfs command
- 4. Bridge forwarding is disabled Bridge forwarding disabled via
- "ebtables -P FORWARD DROP
- In this rather odd situation, the bridge will transmit multicast packets
- (and broadcast) by sending one on each of the slaved interfaces.
- This results in multiple packets through QoS, which is considered "bad".
- To avoid this, multicast/broadcast packets can be marked via ebtables for
- special processing in the NetCP PA module before the packets are queued
- for transmission. Packets thus recognized are NOT marked for egress via a
- specific slave port, and thus will be transmitted through all slave ports
- by the ALE in NetCP switch.
- As part of the pa tx hook in netcp driver, it checks if the interface is
- bridged. If true, it checks if special processing is needed by looking
- at the skb->mark field, it bitwise-ANDs the skb->mark value with the
- "mask" value and then compares the result with the "match" value. If
- these do not match, the mark is ignored and the packet is processed
- normally.
- However, if the "match" value matches, then the low-order 8 bits of the
- skb->mark field is used as a bitmask to determine whether the packet
- should be dropped. If the packet would normally have been directed to
- slave port 1, then bit 0 of skb->mark is checked; slave port 2 checks
- bit 1, etc. If the bit is set, then the packet is enqueued; If the bit
- is NOT set, the packet is silently dropped.
- An example...
- User enter
- echo "12345600 ffffff00" >
- /sys/devices/platform/soc/2620110.netcp/mcast_filter
- The runtime configuration scripts execute this command:
- ebtables -A OUTPUT -d Multicast -j mark \
- --mark-set 0x12345601 --mark-target ACCEPT
- When the bridge attempts to send multicast packet, it will send
- one packet to each of the slave interfaces. The packet sent by the bridge
- to slave interface eth0 (ethss slave port 1) will be passed to the NetCP
- switch, and the ALE will send this packet on all slave ports. The packets
- sent by the bridge to other slave interfaces (eth1, NetCP switch slave
- port 2) will be silently dropped.
- NOTE: This works only when PA is used in the netcp data path
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