Date: Sun, 24 Jun 2018 22:16:38 -0600 From: David Samms <2yt@gmx.com> To: Jim Pingle <lists@pingle.org>, freebsd-stable@freebsd.org Subject: Re: 11.2-RC3 regression - networking igb driver Message-ID: <b78ca11c-a78f-c847-fa09-86a9af069065@gmx.com> In-Reply-To: <2c4e2c6c-ef7a-66a3-e21d-222026c9e88c@pingle.org> References: <2b154303-35f8-df8e-5d2f-ea93b8fdad1d@gmx.com> <2c4e2c6c-ef7a-66a3-e21d-222026c9e88c@pingle.org>
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On 06/24/18 18:30, Jim Pingle wrote: > On 6/23/2018 1:27 PM, David Samms wrote: >> There is a regression in 11.2-RC3 that effects the igb driver for Intels >> C2000 SoC I354 Quad GbE Controller >> >> Supermicro A1SRi-2558F >> http://www.supermicro.com/products/motherboard/Atom/X10/A1SRi-2558F.cfm >> >> This server has run 10.x and 11.x fine up till 11.2-RC3. >> >> PROBLEM: >> with 11.2-RC3 the server boots and gets a network connection to the >> cable modem, but the interface (igb0) resets every 4-8 second. The reset >> time appears to be related to network load, but reset withing 10s with >> next to no traffic. I did try swapping cables, but with no effect. With >> each reset the interface successfully obtains an IP address via DHCP, >> works for a few seconds and resets. >> >> Restoring the server to 11.1-RELEASE-p10 resolves the problem. >> >> Any suggestions? > > Does your DHCP server send you an MTU, perhaps? Before the interface > resets, what does its MTU show? > > You might try creating a dhclient.conf that sets "supersede > interface-mtu 0;" and see if that helps. > > The MTU from DHCP feature is new (see > https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=206721 ) and e1000 > interfaces will reset when applying the MTU. > > Jim P. > Jim, Thank you for your kind reply. I believe you have correctly identified my issue. My ISP is Charter and the modem is a Arris TM822. Running off a live CD of both 11.2-RC3 and 12-CURRENT, I can see that DHCP receives a MTU of 576. In https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=206721 they mention that this is an invalid value, and running dhclient -d, I can see that dhclient considers the value invalid and does reset the interface and makes another request. Interestingly, the interface doesn't appear to actually reset until the new address is received. Manually setting the interface with ifconfig/route, I can ping 8.8.8.8 with MTU of 576, but I didn't try any data transfers. Using ifconfig to set MTU 1500 works fine too. All said, I think we have a rather poor DHCP client in 11.2 and a BREAKING change for many casual users. At the very least, dhclient should be complaining of invalid values being received, that would help the user recover quickly. As of now, all you see in the log is that the interface reset. Ideally dhclient would log the invalid MTU as an error but continue as it did in 11.1 with a valid MTU. Again, thank you for taking the time to help me figure out this puzzle. I am on holiday for the next 5 days and will not be on the internet so won't be able to reply for a while. -- David Samms
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