RE: [PATCH net 1/2] net/mlx4_en: Change min MTU size to ETH_MIN_MTU
flat view
From: David Laight <hidden>
Date: 2018-12-04 16:59:11
From: Tariq Toukan
Sent: 02 December 2018 12:35 From: Eran Ben Elisha <redacted> NIC driver minimal MTU size shall be set to ETH_MIN_MTU, as defined in the RFC791 and in the network stack. Remove old mlx4_en only define for it, which was set to wrong value.
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quoted hunk ↗ jump to hunk
- /* MTU range: 46 - hw-specific max */ - dev->min_mtu = MLX4_EN_MIN_MTU; + /* MTU range: 68 - hw-specific max */ + dev->min_mtu = ETH_MIN_MTU; dev->max_mtu = priv->max_mtu;
Where does 68 come from? The minimum size of an ethernet packet including the mac addresses and CRC is 64 bytes - but that would never be an 'mtu'. Since 64 - 46 = 18, the 46 probably excludes both MAC addresses, the ethertype/length and the CRC. This is 'sort of' the minimum mtu for an ethernet frame. I'm not sure which values are supposed to be in dev->min/max_mtu. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)