diff options
Diffstat (limited to 'Documentation/networking')
| -rw-r--r-- | Documentation/networking/ethtool-netlink.rst | 6 | ||||
| -rw-r--r-- | Documentation/networking/scaling.rst | 15 |
2 files changed, 20 insertions, 1 deletions
diff --git a/Documentation/networking/ethtool-netlink.rst b/Documentation/networking/ethtool-netlink.rst index 6a49624a9cbf..d583d9abf2f8 100644 --- a/Documentation/networking/ethtool-netlink.rst +++ b/Documentation/networking/ethtool-netlink.rst @@ -1774,12 +1774,16 @@ Kernel response contents: ``ETHTOOL_A_RSS_HFUNC`` u32 RSS hash func ``ETHTOOL_A_RSS_INDIR`` binary Indir table bytes ``ETHTOOL_A_RSS_HKEY`` binary Hash key bytes + ``ETHTOOL_A_RSS_INPUT_XFRM`` u32 RSS input data transformation ===================================== ====== ========================== ETHTOOL_A_RSS_HFUNC attribute is bitmap indicating the hash function being used. Current supported options are toeplitz, xor or crc32. -ETHTOOL_A_RSS_INDIR attribute returns RSS indrection table where each byte +ETHTOOL_A_RSS_INDIR attribute returns RSS indirection table where each byte indicates queue number. +ETHTOOL_A_RSS_INPUT_XFRM attribute is a bitmap indicating the type of +transformation applied to the input protocol fields before given to the RSS +hfunc. Current supported option is symmetric-xor. PLCA_GET_CFG ============ diff --git a/Documentation/networking/scaling.rst b/Documentation/networking/scaling.rst index 03ae19a689fc..4eb50bcb9d42 100644 --- a/Documentation/networking/scaling.rst +++ b/Documentation/networking/scaling.rst @@ -44,6 +44,21 @@ by masking out the low order seven bits of the computed hash for the packet (usually a Toeplitz hash), taking this number as a key into the indirection table and reading the corresponding value. +Some NICs support symmetric RSS hashing where, if the IP (source address, +destination address) and TCP/UDP (source port, destination port) tuples +are swapped, the computed hash is the same. This is beneficial in some +applications that monitor TCP/IP flows (IDS, firewalls, ...etc) and need +both directions of the flow to land on the same Rx queue (and CPU). The +"Symmetric-XOR" is a type of RSS algorithms that achieves this hash +symmetry by XORing the input source and destination fields of the IP +and/or L4 protocols. This, however, results in reduced input entropy and +could potentially be exploited. Specifically, the algorithm XORs the input +as follows:: + + # (SRC_IP ^ DST_IP, SRC_IP ^ DST_IP, SRC_PORT ^ DST_PORT, SRC_PORT ^ DST_PORT) + +The result is then fed to the underlying RSS algorithm. + Some advanced NICs allow steering packets to queues based on programmable filters. For example, webserver bound TCP port 80 packets can be directed to their own receive queue. Such “n-tuple” filters can |