path: root/doc/guides/nics/enic.rst
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authorHyong Youb Kim <>2018-03-07 18:46:55 -0800
committerFerruh Yigit <>2018-03-30 14:08:43 +0200
commit422ba91716a761a5d06b85d2a5dd406616a647bd (patch)
treec973721d621a9ddd323fd3d09c3d6e45466166ce /doc/guides/nics/enic.rst
parentc2fec27b5cb0141496623dd7e5eb4a08b1aacdec (diff)
net/enic: heed the requested max Rx packet size
Currently, enic completely ignores the requested max Rx packet size (rxmode.max_rx_pkt_len). The desired behavior is that the NIC hardware drops packets larger than the requested size, even though they are still smaller than MTU. Cisco VIC does not have such a feature. But, we can accomplish a similar (not same) effect by reducing the size of posted receive buffers. Packets larger than the posted size get truncated, and the receive handler drops them. This is also how the kernel enic driver enforces the Rx side MTU. This workaround works only when scatter mode is *not* used. When scatter is used, there is currently no way to support rxmode.max_rx_pkt_len, as the NIC always receives packets up to MTU. For posterity, add a copious amount of comments regarding the hardware's drop/receive behavior with respect to max/current MTU. Signed-off-by: Hyong Youb Kim <> Reviewed-by: John Daley <>
Diffstat (limited to 'doc/guides/nics/enic.rst')
1 files changed, 1 insertions, 0 deletions
diff --git a/doc/guides/nics/enic.rst b/doc/guides/nics/enic.rst
index 4dffce1..0e655e9 100644
--- a/doc/guides/nics/enic.rst
+++ b/doc/guides/nics/enic.rst
@@ -371,6 +371,7 @@ Known bugs and unsupported features in this release
- Setting of extended VLAN
- UDP RSS hashing
- MTU update only works if Scattered Rx mode is disabled
+- Maximum receive packet length is ignored if Scattered Rx mode is used