Description of problem:

alx/ethernet card can't send packet larger than 750 bytes. Receiving works.


Simple tested (using MTU 1500 - DEAFULT!):

*** Works (packet size 750) ****
(yeah, second system is debian, but i'm testing this from fedora with alx)


morsik ~> printf "=%.0s" {1..698} | nc 10.42.0.173 22
SSH-2.0-OpenSSH_6.0p1 Debian-4+deb7u1
Ncat: Connection reset by peer.

16:30:30.553413 IP (tos 0x0, ttl 64, id 17133, offset 0, flags [DF], proto TCP (6), length 750)
    10.42.0.1.60147 > 10.42.0.173.ssh: Flags [P.], cksum 0x44cc (correct), seq 1:699, ack 1, win 229, options [nop,nop,TS val 178983430 ecr 761911], length 698
E...B.@.@...
*..
*........P.f.......D......

......7==========================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================


**** Hang (packet size 751) ****


morsik ~> printf "=%.0s" {1..699} | nc 10.42.0.173 22
SSH-2.0-OpenSSH_6.0p1 Debian-4+deb7u1


16:31:15.426724 IP (tos 0x0, ttl 64, id 25273, offset 0, flags [DF], proto TCP (6), length 751)
    10.42.0.1.60155 > 10.42.0.173.ssh: Flags [P.], cksum 0x39e1 (correct), seq 1:700, ack 40, win 229, options [nop,nop,TS val 179028304 ecr 772757], length 699
E...b.@.@..N
*..
*......Vz.{..!I....9......

..P....===========================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================

Second system (probably - i can't check cause i can't install tcpdump there because… my laptop with alx was router for that debian box and now network via alx doesn't works anymore :P) doesn't receive packet, cause my Fedora tried to resend TCP packet few times cause it things that remote system lost packet.

Chaing MTU do 750 "fixes" this bug, but of course packet is smaller so it's less space for payload.



Version-Release number of selected component (if applicable):
kernel-3.16.6-203.fc20.x86_64

I reinstalled to Fedora from ArchLinux few days ago. On archlinux i had linux-3.16.4-1 which WORKED.


How reproducible:
Always.


Steps to Reproduce:
As above.


Actual results:
Packets don't reach destination.


Expected results:
Packets should reach destination without any problem


Additional info:

xwing.darkhouse ~> lspci -knn | grep -iA3 ether
02:00.0 Ethernet controller [0200]: Qualcomm Atheros AR8161 Gigabit Ethernet [1969:1091] (rev 08)
	Subsystem: Lenovo Device [17aa:3979]
	Kernel driver in use: alx
	Kernel modules: alx


The system is sleeping from time to time! I'm writing this cause I read about some problems with sleeping on alx driver. But I've tried `rmmod alx; modprobe alx` after resume — didn't helped.