netdev - Re: Poor thunderbolt-net interface performance when bridged

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Message-Id: <8672A9A1-6B32-4F81-8DFA-4122A057C9BE@bejarano.io>
Date: Tue, 27 May 2025 16:25:16 +0200
From: Ricard Bejarano <ricard@...arano.io>
To: Andrew Lunn <andrew@...n.ch>
Cc: Mika Westerberg <mika.westerberg@...ux.intel.com>,
 netdev@...r.kernel.org,
 michael.jamet@...el.com,
 YehezkelShB@...il.com,
 andrew+netdev@...n.ch,
 davem@...emloft.net,
 edumazet@...gle.com,
 kuba@...nel.org,
 pabeni@...hat.com
Subject: Re: Poor thunderbolt-net interface performance when bridged

Ok, I was going mad trying to find CRC stats for blue's tb0.

'ethtool -S' returns "no stats available".
'netstat' and 'ss' aren't much better than 'ip -s link show dev'.
CRC verification is done by the driver so 'tcpdump' won't see those (I do see loss, however).

But, I do see the thunderbolt-net driver exposes rx_crc_errors.
And then I found 'ip -s -s' (double -s):

root@...e:~# ip -s -s link show dev tb0
5: tb0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel master br0 state UP mode DEFAULT group default qlen 1000
    link/ether 02:70:19:dc:92:96 brd ff:ff:ff:ff:ff:ff
    RX:  bytes packets errors dropped  missed   mcast           
    9477191497 6360635  16763       0       0       0 
    RX errors:  length    crc   frame    fifo overrun
                     0  16763       0       0       0 
    TX:  bytes packets errors dropped carrier collsns           
          8861     100      0       0       0       0 
    TX errors: aborted   fifo  window heartbt transns
                     0      0       0       0       2 
root@...e:~# 

Bingo! CRC errors.

How can we proceed?

Thanks,
RB