On Tue, 10 Dec 2019 12:46:29 +0100, Maciej Żenczykowski wrote: > > Okay, that's what I was suspecting. It'd be great if the real > > motivation for a patch was spelled out in the commit message :/ > > It is, but the commit message is already extremely long. Long, yet it doesn't mention the _real_ reason for the patch. > At some point essays and discussions belong in email and not in the > commit message. Ugh just admit you didn't mention the primary use case in the commit log, and we can move on. > Here's another use case: > > A network where firewall policy or network behaviour blocks all > traffic using specific ports. > > I've seen generic firewalls that unconditionally drop all BGP or SMTP > port traffic, or all traffic on ports 5060/5061 (regardless of > direction) or on 25/53/80/123/443/853/3128/8000/8080/8088/8888 > (usually due to some ill guided security policies against sip or open > proxies or xxx). If you happen to use port XXXX as your source port > your connection just hangs (packets are blackholed). > > Sure you can argue the network is broken, but in the real world you > often can't fix it... Go try and convince your ISP that they should > only drop inbound connections to port 8000, but not outgoing > connections from port 8000 - you'll go crazy before you find someone > who even understands what you're talking about - and even if you find > such a person, they'll probably be too busy to change things - and > even though it might be a 1 letter change (port -> dport) - it still > might take months of testing and rollout before it's fully deployed. > > I've seen networks where specific ports are automatically classified > as super high priority (network control) so you don't want anything > using these ports without very good reason (common for BGP for > example, or for encap schemes). > > Or a specific port number being reserved by GUE or other udp encap > schemes and thus unsafe to use for generic traffic (because the > network or even the kernel itself might for example auto decapsulate > it [via tc ebpf for example], or parse the interior of the packet for > flowhashing purposes...). > > [I'll take this opportunity to point out that due to poor flow hashing > behaviour GRE is basically unusable at scale (not to mention poorly > extensible), and thus GUE and other UDP encap schemes are taking over] > > Or you might want to forward udp port 4500 from your external IP to a > dedicated ipsec box or some hardware offload engine... etc. It's networking you can concoct a scenario to justify anything. > > So some SoCs which run non-vanilla kernels require hacks to steal > > ports from the networking stack for use by proprietary firmware. > > I don't see how merging this patch benefits the community. > > I think you're failing to account for the fact that the majority of > Linux users are Android users - there's around 2.5 billion Android > phones in the wild... - but perhaps you don't consider your users (or > Android?) to be part of your community? I don't consider users of non-vanilla kernels to necessarily be a reason to merge patches upstream, no. They carry literally millions of lines of patches out of tree, let them carry this patch, too. If I can't boot a vanilla kernel on those devices, and clearly there is no intent by the device manufacturers for me to ever will, why would I care? Some companies care about upstream, and those should be rewarded by us taking some of the maintenance off their hands. Some don't: https://www.youtube.com/watch?v=_36yNWw_07g (link to Linus+nVidia video) even tho they sell majority of SoCs for 2.5 billion devices. > btw. Chrome OS is also Linux based (and if a quick google search is to > be believed, about 1/7th of the linux desktop/laptop share), but since > it supports running Android apps, it needs to have all Android > specific generic kernel changes... > > The reason Android runs non-vanilla kernels is *because* patches like > this - that make Linux work in the real world - are missing from > vanilla Linux > (I can think of a few other networking patches off the top of my head > where we've been unable to upstream them for no particularly good > reason). The way to get those patches upstream is to have a honest discussion about the use case so people can validate the design. Not by sending a patch with a 5 page commit message which fails to clearly state the motivation for the feature :/
