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Diffstat (limited to 'Documentation/networking/scaling.rst')
| -rw-r--r-- | Documentation/networking/scaling.rst | 15 |
1 files changed, 11 insertions, 4 deletions
diff --git a/Documentation/networking/scaling.rst b/Documentation/networking/scaling.rst index 4eb50bcb9d42..6984700cec6a 100644 --- a/Documentation/networking/scaling.rst +++ b/Documentation/networking/scaling.rst @@ -49,14 +49,21 @@ 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 +"Symmetric-XOR" and "Symmetric-OR-XOR" are types of RSS algorithms that +achieve this hash symmetry by XOR/ORing 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 "Symmetric-XOR" algorithm XORs the input as follows:: # (SRC_IP ^ DST_IP, SRC_IP ^ DST_IP, SRC_PORT ^ DST_PORT, SRC_PORT ^ DST_PORT) +The "Symmetric-OR-XOR" algorithm, on the other hand, transforms 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 |