Ethernet eth0: len 1571 larger than size (1536)

vanyaindigo · February 25, 2019, 7:55am

Can anyone explain what this error is and how to solve it?

Mon Feb 25 08:41:08 2019 kern.err kernel: [185448.296693] ipq806x-gmac-dwmac 37200000.ethernet eth0: len 1571 larger than size (1536)
Mon Feb 25 08:41:09 2019 kern.err kernel: [185449.315566] ipq806x-gmac-dwmac 37200000.ethernet eth0: len 1571 larger than size (1536)
Mon Feb 25 08:41:10 2019 kern.err kernel: [185450.346098] ipq806x-gmac-dwmac 37200000.ethernet eth0: len 1571 larger than size (1536)
Mon Feb 25 08:41:11 2019 kern.err kernel: [185451.039917] ipq806x-gmac-dwmac 37200000.ethernet eth0: len 1571 larger than size (1536)
Mon Feb 25 08:41:11 2019 kern.err kernel: [185451.238042] ipq806x-gmac-dwmac 37200000.ethernet eth0: len 1571 larger than size (1536)
Mon Feb 25 08:41:11 2019 kern.err kernel: [185451.963553] ipq806x-gmac-dwmac 37200000.ethernet eth0: len 1571 larger than size (1536)
Mon Feb 25 08:41:12 2019 kern.err kernel: [185452.266806] ipq806x-gmac-dwmac 37200000.ethernet eth0: len 1571 larger than size (1536)
Mon Feb 25 08:41:12 2019 kern.err kernel: [185452.412514] ipq806x-gmac-dwmac 37200000.ethernet eth0: len 1571 larger than size (1536)
Mon Feb 25 08:41:12 2019 kern.err kernel: [185452.464056] ipq806x-gmac-dwmac 37200000.ethernet eth0: len 1571 larger than size (1536)
Mon Feb 25 08:41:13 2019 kern.err kernel: [185453.331352] ipq806x-gmac-dwmac 37200000.ethernet eth0: len 1571 larger than size (1536)
Mon Feb 25 08:41:13 2019 kern.err kernel: [185453.545645] ipq806x-gmac-dwmac 37200000.ethernet eth0: len 1571 larger than size (1536)
Mon Feb 25 08:41:15 2019 kern.err kernel: [185455.372171] ipq806x-gmac-dwmac 37200000.ethernet eth0: len 1571 larger than size (1536)
Mon Feb 25 08:41:15 2019 kern.err kernel: [185455.697899] ipq806x-gmac-dwmac 37200000.ethernet eth0: len 1571 larger than size (1536)
Mon Feb 25 08:41:16 2019 kern.err kernel: [185456.560718] ipq806x-gmac-dwmac 37200000.ethernet eth0: len 1571 larger than size (1536)
Mon Feb 25 08:41:19 2019 kern.err kernel: [185459.471881] ipq806x-gmac-dwmac 37200000.ethernet eth0: len 1571 larger than size (1536)
Mon Feb 25 08:41:19 2019 kern.err kernel: [185459.877131] ipq806x-gmac-dwmac 37200000.ethernet eth0: len 1571 larger than size (1536)
Mon Feb 25 08:41:23 2019 kern.err kernel: [185463.866693] ipq806x-gmac-dwmac 37200000.ethernet eth0: len 1571 larger than size (1536)
Mon Feb 25 08:41:23 2019 kern.err kernel: [185463.871237] ipq806x-gmac-dwmac 37200000.ethernet eth0: len 1571 larger than size (1536)

moeller0 · February 25, 2019, 1:34pm

Silly question, are you using sqm-scripts or qos-scropts by any chance?

vanyaindigo · February 25, 2019, 1:37pm

As far as I understand, none of this I've set up

jeff · February 25, 2019, 1:40pm

My guess would be something on your network is sending oversized Ethernet packets either malformed or your router isn’t configured for jumbo frames.

vanyaindigo · February 25, 2019, 1:44pm

I'll try to dig in this direction thanks

jeff · February 25, 2019, 2:10pm

See also https://bugs.openwrt.org/index.php?do=details&task_id=2026 kernel ipq806x Oops

which shows, in its log

Wed Dec 26 18:09:06 2018 kern.err kernel: [ 1488.045291] ipq806x-gmac-dwmac 37200000.ethernet eth0: len 1990 larger than size (1536)

(Not clear that there is a solution there, just came across it on the openwrt-devel mailing list)

ewald · March 1, 2019, 5:00pm

@vanyaindigo,
It's caused by a combination of two things:

a device on your network sending packages larger than the router's default MTU of 1500 (a network packet > 1536 bytes). It's possible that none of your devices have Jumbo packets enabled, but that a device simply misbehaves. This causes the driver to log the error message you posted
a series of (known) kernel driver defects in the ST Micro ethernet switch core code stmmac_main.c (see kernel stmmac_main.c commits). These defects will cause a kernel panic after a (undefined) number of these errors (freeing memory that was not allocated by the driver).

There are two tested and proven "solutions":

set your MTU to 9000 in /etc/rc.local. This will both stop the error as well as bypass the main defect that causes the kernel to panic. It's the easy route...
use a pre-release of OpenWrt based on kernel 4.19 or compile your own version 18.06 with back-ported kernel 4.19 fixes (or wait for an official release based on 4.19 kernel)