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Author Topic: BCM63168 Modems that Support Baby Jumbo Frames (Bridge Mode)  (Read 81357 times)

Weaver

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Re: BCM63168 Modems that Support Baby Jumbo Frames (Bridge Mode)
« Reply #60 on: May 04, 2018, 03:31:07 PM »

I would love to try this fw out, the MTU thing was putting me off using the 1312-B10A. Also, I would need to get two more B10As from somewhere as I have three lines but only one modem currently (which the ISP AA sold me).

Mind you, there is still the PPP session drop bug - https://support.aa.net.uk/VMG1312-B10A:_Bugs - which affects AA users but if I understand correctly not some other ISPs because that article says it is determined by whether or not the ISP uses a static WAN IP address, which AA always does.
« Last Edit: May 04, 2018, 03:40:40 PM by Weaver »
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j0hn

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Re: BCM63168 Modems that Support Baby Jumbo Frames (Bridge Mode)
« Reply #61 on: May 04, 2018, 04:29:55 PM »

The PPP session drop bug only affects the device when used as a modem router.

Used in bridge mode with your Firebrick you would have no such issue.

Have you compared the Zyxels sync rate with your current modem?
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j0hn

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Re: BCM63168 Modems that Support Baby Jumbo Frames (Bridge Mode)
« Reply #62 on: May 07, 2018, 04:00:10 PM »

The 8924 firmware image from Zyxel for anyone who wants it. It's the V1.00(AAKL.21)C0 firmware.
I see no reason this won't work with the 8924 the same as it does for the 1312.
I'll have a go at building the firmware image tomorrow.

https://www.dropbox.com/sh/3kefsh7qo5yuixm/AABT4xceivGrYBTsz4pNDz5ya?dl=0

The link expires on May 13th 2018
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Weaver

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Re: BCM63168 Modems that Support Baby Jumbo Frames (Bridge Mode)
« Reply #63 on: May 07, 2018, 11:15:43 PM »

So should I go for it, try my B10A out, if I can find it? With the custom firmware. It will be in straight-modem only mode in my case. As I said earlier, I've been very keen on getting PPP MTU 1508 support and RFC 4638.

And just to sanity check, PPP bug if used as a router but not if modem-only?

Burakkucat, you mentioned that you have one I think. I can't remember if yours is being used as just a modem or a router. It's rather a lot to ask, but let me know if you are up for testing the fw? Would you have time or inclination to build it even?

Does someone have cross-compiler tools then?

Could I also get some help reflashing it? (drugs)

Also so help with configuring it afterwards. (more drugs) For example I need to get it into modem-only + G.992.3-only + PPPoEoA VC-MUX no-FCS-preserved mode and get the wireless turned off.
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burakkucat

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Re: BCM63168 Modems that Support Baby Jumbo Frames (Bridge Mode)
« Reply #64 on: May 07, 2018, 11:38:28 PM »

So should I go for it, try my B10A out, if I can find it? With the custom firmware. It will be in straight-modem only mode in my case. As I said earlier, I've been very keen on getting PPP MTU 1508 support and RFC 4638.

If you can (or if you can get some local help), I would say "yes".

Quote
And just to sanity check, PPP bug if used as a router but not if modem-only?

A bridging modem does nothing PPP-wise, so yes, that bug only affects the VMG1312-B10A when used in modem/router mode under certain conditions. I would trust the words of j0hn!

Quote
Burakkucat, you mentioned that you have one I think. I can't remember if yours is being used as just a modem or a router. It's rather a lot to ask, but let me know if you are up for testing the fw? Would you have time or inclination to build it even?

I use my VMG1312-B10A in modem/router mode and it allows me to set the MTU to 1500. Hence I have no need of the customised firmware.

The custom firmware image is available --

Just flash the precompiled firmware from the releases section:

https://github.com/Olipro/VMG1312-B10A/releases

Set your routers wan MTU to 1508 and it just works.

Like I said it worked for me but flash at your own risk.


Quote
Could I also get some help reflashing it? (drugs)

Also so help with configuring it afterwards. (more drugs) For example I need to get it into modem-only + G.992.3-only + PPPoEoA VC-MUX no-FCS-preserved mode and get the wireless turned off.

You really need some help from someone in the same country, Alba.
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Weaver

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Re: BCM63168 Modems that Support Baby Jumbo Frames (Bridge Mode)
« Reply #65 on: May 07, 2018, 11:57:29 PM »

The thing about the bug is that I believe certain usage patterns happened to trigger it despite the fact that as you rightly say, it knows nothing about the details of PPP but this is a PPPoE thing, I was wrong.

“PPPoE Session-ID caching bug (In Bridge mode)” is the entry in AA’s bugs list. So it would affect me under the right usage conditions, to do with constant value of (say UDP) source port and long-term usage if I am understanding correctly. It's an evil hardware higher-level protocol snooping thing, where it should not know anything about such protocols but in fact it sneakily does. Huawei has the same bug.

I don't suppose someone out there could fix that bug, suggested fix strategies are mentioned by AA. I wonder if AA could be given enough source code for them to fix it themselves.
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j0hn

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Re: BCM63168 Modems that Support Baby Jumbo Frames (Bridge Mode)
« Reply #66 on: May 08, 2018, 09:33:49 AM »

Quote
PPPoE Session-ID caching bug (In Bridge mode)
Issue Description
Last year we had an problem with Huawei FTTC modems, the standard ones that Openreach supply The bug appears to be that the modem manages to "blacklist" some UDP packets after a PPP restart. Typically this affects VPN tunnels. The short term fix is to unplugged and plugged back in!

We now have what looks to be the same fault on the ZyXELs - both on ADSL and VDSL.

When a PPPoE session finishes and a new one starts, ethernet frames containing IP packets with the same source and destination IP and port combination that were used in the previous session are received with the PPPoE Session-ID from the earlier session.

This affects long running sessions using protocols which use the same source port for all communications. This includes IPsec and (in some circumstances) SIP.

Our understanding of this, having talked to Huawei last year to get a very similar bug fixed is that the problem is with the packet accelerator feature in the Broadcom chipset. It is caching frame headers including the PPPoE Session-ID, but not checking if the Session-ID is the same when searching for the entry in the cache for subsequent packets. Unplugging the ethernet cable from the VMG1312 momentarily resolves the problem - that action must trigger a cache flush in the Broadcom chipset.

Possible fixes would be to either not store the Session-ID in the packet accelerator cache at all, or to check the Session-ID in addition to the IP and ports when searching the cache. A workaround would be to disable the packet accelerator.

(Side note for other ISPs looking at this: This does not affect lines that have dynamic WAN addresses, which none of our service do.)

This is so obscure it's ridiculous. It's not ZyXEL that need to fix it, it's Broadcom.
It appears to be present in most Broadcom modems.
I use an IPsec VPN a dozen times a day and have never come across this on either the ZyXEL or the Huawei HG612, which I've used for over 5 years between them.

It's the IPV6 bugs that cause lots of issues with the  VMG1312-B10A. They only affect it in router mode.
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johnson

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Re: BCM63168 Modems that Support Baby Jumbo Frames (Bridge Mode)
« Reply #67 on: May 08, 2018, 12:10:50 PM »

So should I go for it, try my B10A out, if I can find it?

It worked on mine, and was up for several days before I went back to an older firmware for unrelated issues. So no problems using it and then going back to something different, all just flashing through the web interface.

Of course for peace of mind getting the originals from zyxel and setting up the build environment would be better.

On a related note, does anyone recall people changing out the dsl driver on similar firmwares? I have vague memories of people changing out the broadcom 39'x' dsl driver portion of the firmware in order to get newer versions on HG612s and maybe others. I think I have found issues with newer versions of the BCM code and frankensteining together the 1508 patches with an older driver would be great.
« Last Edit: May 08, 2018, 12:13:31 PM by johnson »
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burakkucat

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Re: BCM63168 Modems that Support Baby Jumbo Frames (Bridge Mode)
« Reply #68 on: May 08, 2018, 04:03:59 PM »

On a related note, does anyone recall people changing out the dsl driver on similar firmwares? I have vague memories of people changing out the broadcom 39'x' dsl driver portion of the firmware in order to get newer versions on HG612s and maybe others. I think I have found issues with newer versions of the BCM code and frankensteining together the 1508 patches with an older driver would be great.

It was back in November 2012 that asbokid documented a series of experiments in which he tested the result of dynamically swapping-out the hardware driver's blob, i.e. the driver's firmware, and not the driver itself. I think I have a copy of his report stashed away, somewhere.
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Weaver

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Re: BCM63168 Modems that Support Baby Jumbo Frames (Bridge Mode)
« Reply #69 on: May 09, 2018, 12:06:39 AM »

When they supply a binary blob, they presumably don't trust their customer with the source code in case they rip it off or fiddle around with it, quite understandable.

Do they have a vector table of entries into it at a documented offset, or use a kind of standard dynamic library format ?
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burakkucat

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Re: BCM63168 Modems that Support Baby Jumbo Frames (Bridge Mode)
« Reply #70 on: May 09, 2018, 12:20:21 AM »

When they supply a binary blob, they presumably don't trust their customer with the source code in case they rip it off or fiddle around with it, quite understandable.

Yes, I suspect that is the case.

Quote
Do they have a vector table of entries into it at a documented offset, or use a kind of standard dynamic library format ?

Sorry, I do not have any knowledge of the (xDSL driver's) blob format. There is one person who might have studied such entities or who might have an opinion and that is ejs.
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spring

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Re: BCM63168 Modems that Support Baby Jumbo Frames (Bridge Mode)
« Reply #71 on: May 11, 2018, 04:06:13 AM »

Replaced AAJZ.11 with this custom AAJZ.14, didn't reconfigure, sent "ifconfig ppp2.1 mtu 1500" in telnet and didn't notice a problem for the past 2 days (modem-router mode).

But, it only lasts for the PPP session, and next session reverts back to 1492.

I don't know what can be done as I'm clueless about these things.
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Weaver

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Re: BCM63168 Modems that Support Baby Jumbo Frames (Bridge Mode)
« Reply #72 on: May 11, 2018, 08:09:35 AM »

Sorry, I'm not following spring, what happens when you just boot that firmware straight up without doing anything at all to configure things?
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spring

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Re: BCM63168 Modems that Support Baby Jumbo Frames (Bridge Mode)
« Reply #73 on: May 11, 2018, 03:32:15 PM »

Pinging 1472 [+28 = 1500] without fragmentation doesn't work, why else would I say it reverts back.
« Last Edit: May 11, 2018, 03:36:16 PM by spring »
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Weaver

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Re: BCM63168 Modems that Support Baby Jumbo Frames (Bridge Mode)
« Reply #74 on: May 11, 2018, 04:21:33 PM »

So this mod only works temporarily?
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