On Mon, Oct 28, 2019 at 02:05:24PM -0700, John Fastabend wrote: > Martin Lau wrote: > > On Mon, Oct 28, 2019 at 01:35:26PM +0100, Jakub Sitnicki wrote: > > > On Mon, Oct 28, 2019 at 06:52 AM CET, Martin Lau wrote: > > > > On Tue, Oct 22, 2019 at 01:37:25PM +0200, Jakub Sitnicki wrote: > > > >> This patch set is a follow up on a suggestion from LPC '19 discussions to > > > >> make SOCKMAP (or a new map type derived from it) a generic type for storing > > > >> established as well as listening sockets. > > > >> > > > >> We found ourselves in need of a map type that keeps references to listening > > > >> sockets when working on making the socket lookup programmable, aka BPF > > > >> inet_lookup [1]. Initially we repurposed REUSEPORT_SOCKARRAY but found it > > > >> problematic to extend due to being tightly coupled with reuseport > > > >> logic (see slides [2]). > > > >> So we've turned our attention to SOCKMAP instead. > > > >> > > > >> As it turns out the changes needed to make SOCKMAP suitable for storing > > > >> listening sockets are self-contained and have use outside of programming > > > >> the socket lookup. Hence this patch set. > > > >> > > > >> With these patches SOCKMAP can be used in SK_REUSEPORT BPF programs as a > > > >> drop-in replacement for REUSEPORT_SOCKARRAY for TCP. This can hopefully > > > >> lead to code consolidation between the two map types in the future. > > > > What is the plan for UDP support in sockmap? > > > > > > It's on our road-map because without SOCKMAP support for UDP we won't be > > > able to move away from TPROXY [1] and custom SO_BINDTOPREFIX extension > > > [2] for steering new UDP flows to receiving sockets. Also we would like > > > to look into using SOCKMAP for connected UDP socket splicing in the > > > future [3]. > > > > > > I was planning to split work as follows: > > > > > > 1. SOCKMAP support for listening sockets (this series) > > > 2. programmable socket lookup for TCP (cut-down version of [4]) > > > 3. SOCKMAP support for UDP (work not started) > > hmm...It is hard to comment how the full UDP sockmap may > > work out without a code attempt because I am not fluent in > > sock_map ;) > > > > From a quick look, it seems there are quite a few things to do. > > For example, the TCP_SKB_CB(skb) usage and how that may look > > like in UDP. "struct udp_skb_cb" is 28 bytes while "struct napi_gro_cb" > > seems to be 48 bytes already which may need a closer look. > > The extra bits sockmap needs are used for redirecting between > between sockets. These will fit in the udp cb area with some > extra room to spare. If that is paticularly challenging we can > also create a program attach type which would preclude using > those bits in the sk_reuseport bpf program types. We already > have types for rx, tx, nop progs, so one more should be fine. > > So at least that paticular concern is not difficult to fix. > > > > > > 4. programmable socket lookup for UDP (rest of [4]) > > > > > > I'm open to suggestions on how to organize it. > > > > > > >> Having said that, the main intention here is to lay groundwork for using > > > >> SOCKMAP in the next iteration of programmable socket lookup patches. > > > > What may be the minimal to get only lookup work for UDP sockmap? > > > > .close() and .unhash()? > > > > > > John would know better. I haven't tried doing it yet. > > > > > > From just reading the code - override the two proto ops you mentioned, > > > close and unhash, and adapt the socket checks in SOCKMAP. > > Do your use cases need bpf prog attached to sock_map? > > Perhaps not specifically sock_map but they do need to be consolidated > into a map somewhere IMO this has proven to be the most versatile. We > can add sockets from the various BPF hooks or from user space and have > the ability to use the existing map tools, etc. > > > > > If not, would it be cleaner to delicate another map_type > > for lookup-only use case to have both TCP and UDP support. > > But we (Cilium project and above splicing use case is also interested) > will need UDP support so it will be supported regardless of the > SK_REUSEPORT_BPF so I think it makes sense to consolidate all these > use cases on to the existing sockmap. > > Also sockmap supports inserting sockets from BPF and from userspace > which actually requires a bit of logic to track state, etc. Its been > in use and been beat on by various automated test tools so I think > at minimum this needs to be reused. Re-implementing this logic seems > a waste of time and it wasn't exactly trivial and took some work. > > Being able to insert the sockets from XDP (support coming soon) and > from sock_ops programs turns out to be fairly powerful. > > So in short I think it makes most sense to consolidate on sock_map > because > > (a) we need and will add udp support regardless, > (b) we already handle the tricky parts inerting/removing live sockets I didn't mean not to reuse the existing sockmap logic on tracking socks life-time. I was exploring options if the first step for UDP could be lookup-only support first. It is always better to get full UDP support ;) It seems to be confident also, then there is little reason not to do so in UDP sockmap support v1. > (c) from this series it looks like its fairly straight forward > (d) we get lots of shared code > > Thanks, > John > > > > > > > > > > -Jakub > > > > > > [1] https://urldefense.proofpoint.com/v2/url?u=https-3A__blog.cloudflare.com_how-2Dwe-2Dbuilt-2Dspectrum_&d=DwIBAg&c=5VD0RTtNlTh3ycd41b3MUw&r=VQnoQ7LvghIj0gVEaiQSUw&m=lSo-FsOeNl_8znZZ07H8I6ZYAinPKTR5C3Cn_Ol3QYQ&s=DZgW8-2Xl1P8NU59ji4ieQLzwWpx4t3gGq_tqB0l3Bo&e= > > > [2] https://lore.kernel.org/netdev/1458699966-3752-1-git-send-email-gilberto.bertin@xxxxxxxxx/ > > > [3] https://lore.kernel.org/bpf/20190828072250.29828-1-jakub@xxxxxxxxxxxxxx/ > > > [4] https://urldefense.proofpoint.com/v2/url?u=https-3A__blog.cloudflare.com_sockmap-2Dtcp-2Dsplicing-2Dof-2Dthe-2Dfuture_&d=DwIBAg&c=5VD0RTtNlTh3ycd41b3MUw&r=VQnoQ7LvghIj0gVEaiQSUw&m=lSo-FsOeNl_8znZZ07H8I6ZYAinPKTR5C3Cn_Ol3QYQ&s=NerUqb4j7IsGBTcni6Yxk40wf6kTkckHXn3Nx5i4mCU&e= > >
