Date: Fri, 28 Dec 2007 20:40:30 +0100 From: Marko Zec <zec@tel.fer.hr> To: freebsd-arch@freebsd.org, FreeBSD Net <freebsd-net@freebsd.org> Cc: gnn@freebsd.org, Robert Watson <rwatson@freebsd.org>, Julian Elischer <julian@elischer.org>, Qing Li <qingli@freebsd.org> Subject: Re: resend: multiple routing table roadmap (format fix) Message-ID: <200712282040.30745.zec@tel.fer.hr> In-Reply-To: <m2bq8bvsis.wl%gnn@neville-neil.com> References: <4772F123.5030303@elischer.org> <m2bq8bvsis.wl%gnn@neville-neil.com>
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On Friday 28 December 2007 14:49:15 gnn@freebsd.org wrote: > At Wed, 26 Dec 2007 16:26:11 -0800, > > julian wrote: > > > > On thing where FreeBSD has been falling behind, and which by chance > > I have some time to work on is "policy based routing", which allows > > different packet streams to be routed by more than just the > > destination address. > > > > Constraints: > > ------------ > > > > I want to make some form of this available in the 6.x tree > > (and by extension 7.x) , but FreeBSD in general needs it so I might > > as well > > do it in -current and back port the portions I need. > > > > One of the ways that this can be done is to have the ability to > > instantiate multiple kernel routing tables (which I will now > > refer to as "Forwarding Information Bases" or "FIBs" for political > > correctness reasons. Which FIB a particular packet uses to make > > the next hop decision can be decided by a number of mechanisms. > > The policies these mechanisms implement are the "Policies" referred > > to in "Policy based routing". > > > > One of the constraints I have if I try to back port this work to > > 6.x is that it must be implemented as a EXTENSION to the existing > > ABIs in 6.x so that third party applications do not need to be > > recompiled in timespan of the branch. > > > > Implementation method, (part 1) > > ------------------------------- > > For this reason I have implemented a "sufficient subset" of a > > multiple routing table solution in Perforce, and back-ported it > > to 6.x. (also in Perforce though not yet caught up with what I > > have done in -current/P4). The subset allows a number of FIBs > > to be defined at compile time (sufficient for my purposes in 6.x) > > and implements the changes needed to allow IPV4 to use them. I have > > not done the changes for ipv6 simply because I do not need it, and > > I do not have enough knowledge of ipv6 (e.g. neighbor discovery) > > needed to do it. > > > > Other protocol families are left untouched and should there be > > users with proprietary protocol families, they should continue to > > work and be oblivious to the existence of the extra FIBs. > > > > To understand how this is done, one must know that the current FIB > > code starts everything off with a single dimensional array of > > pointers to FIB head structures (One per protocol family), each of > > which in turn points to the trie of routes available to that > > family. > > > > The basic change in the ABI compatible version of the change is to > > extent that array to be a 2 dimensional array, so that > > instead of protocol family X looking at rt_tables[X] for the > > table it needs, it looks at rt_tables[Y][X] when for all > > protocol families except ipv4 Y is always 0. > > Code that is unaware of the change always just sees the first row > > of the table, which of course looks just like the one dimensional > > array that existed before. > > > > > > The entry points rtrequest(), rtalloc(), rtalloc1(), rtalloc_ign() > > are all maintained, but refer only to the first row of the array, > > so that existing callers in proprietary protocols can continue to > > do the "right thing". > > Some new entry points are added, for the exclusive use of ipv4 code > > called in_rtrequest(), in_rtalloc(), in_rtalloc1() and > > in_rtalloc_ign(), which have an extra argument which refers the > > code to the correct row. > > > > In addition, there are some new entry points (currently called > > dom_rtalloc() and friends) that check the Address family being > > looked up and call either rtalloc() (and friends) if the protocol > > is not IPv4 forcing the action to row 0 or to the appropriate row > > if it IS IPv4 (and that info is available). These are for calling > > from code that is not specific to any particular protocol. The way > > these are implemented would change in the non ABI preserving code > > to be added later. > > > > One feature of the first version of the code is that for ipv4, > > the interface routes show up automatically on all the FIBs, so > > that no matter what FIB you select you always have the basic > > direct attached hosts available to you. (rtinit() does this > > automatically). > > You CAN delete an interface route from one FIB should you want > > to but by default it's there. ARP information is also available > > in each FIB. It's assumed that the same machine would have the > > same MAC address, regardless of which FIB you are using to get > > to it. > > > > > > This brings us as to how the correct FIB is selected for an > > outgoing IPV4 packet. > > > > Packets fall into one of a number of classes. > > 1/ locally generated packets, coming from a socket/PCB. > > Such packets select a FIB from a number associated with the > > socket/PCB. This in turn is inherited from the process, > > but can be changed by a socket option. The process in turn > > inherits it on fork. I have written a utility call setfib > > that acts a bit like nice.. > > > > setfib -n 3 ping target.example.com # will use fib 3 for > > ping. > > > > 2/ packets received on an interface for forwarding. > > By default these packets would use table 0, > > (or possibly a number settable in a sysctl(not yet)). > > but prior to routing the firewall can inspect them (see below). > > > > 3/ packets inspected by a packet classifier, which can arbitrarily > > associate a fib with it on a packet by packet basis. > > A fib assigned to a packet by a packet classifier > > (such as ipfw) would over-ride a fib associated by > > a more default source. (such as cases 1 or 2). > > > > Routing messages would be associated with their > > process, and thus select one FIB or another. > > > > In addition Netstat has been edited to be able to cope with the > > fact that the array is now 2 dimensional. (It looks in system > > memory using libkvm (!)). > > > > In addition two sysctls are added to give: > > a) the number of FIBs compiled in (active) > > b) the default FIB of the calling process. > > > > Early testing experience: > > ------------------------- > > > > Basically our (IronPort's) appliance does this functionality > > already using ipfw fwd but that method has some drawbacks. > > > > For example, > > It can't fully simulate a routing table because it can't influence > > the socket's choice of local address when a connect() is done. > > > > > > Testing during the generating of these changes has been > > remarkably smooth so far. Multiple tables have co-existed > > with no notable side effects, and packets have been routes > > accordingly. > > > > I have not yet added the changes to ipfw. > > pf has some similar changes already but they seem to rely on > > the various FIBs having symbolic names. Which I do not plan to > > support in the first version of these changes. > > > > SCTP has interestingly enough built in support for this, called > > VRFs in Cisco parlance. it will be interesting to see how that > > handles it when it suddenly actually does something. > > > > I have not redone my testing since my last edits, but will be > > retesting with the current code asap. > > > > > > Where to next: > > -------------------- > > > > After committing the ABI compatible version and MFCing it, I'd > > like to proceed in a forward direction in -current. this will > > result in some roto-tilling in the routing code. > > > > Firstly: the current code's idea of having a separate tree per > > protocol family, all of the same format, and pointed to by the > > 1 dimensional array is a bit silly. Especially when one considers > > that there > > is code that makes assumptions about every protocol having the same > > internal structures there. Some protocols don't WANT that > > sort of structure. (for example the whole idea of a netmask is > > foreign to appletalk). This needs to be made opaque to the external > > code. > > > > My suggested first change is to add routing method pointers to the > > 'domain' structure, along with information pointing the data. > > instead of having an array of pointers to uniform structures, > > there would be an array pointing to the 'domain' structures > > for each protocol address domain (protocol family), > > and the methods this reached would be called. The methods would > > have an argument that gives FIB number, but the protocol would be > > free to ignore it. > > > > Interaction with the ARP layer/ LL layer would need to be > > revisited as well. Qing Li has been working on this already. > > > > > > diffs > > for those with p4 access: > > p4 diff2 -du //depot/vendor/freebsd/src/sys/...@131121 > > //depot/user/julian/routing/src/sys/... > > > > for those with the makediff perl script: > > perl ~/makediff.pl //depot/vendor/freebsd/src/sys/...@131121 > > //depot/user/julian/routing/src/sys/... > > > > for those with neither: > > > > http://people.freebsd.org/~julian/mrt2.diff > > > > I just put the userland utility in usr.sbin/setfib/ in p4. > > and changes to netstat in usr.bin/netstat/ > > > > see: > > http://perforce.freebsd.org/depotTreeBrowser.cgi?FSPC=//depot/user/ > >julian/routing/src&HIDEDEL=NO > > > > I'd like to get comments on this (compat) version, so that I can > > commit it, get general testing under way to start the clock for > > MFC, and then get moving on the fuller implementation (that breaks > > ABIs) and other routing issues. > > How does this work with Marko Zec's virtual stack system? The thrust behind Julian's work seems to be providing multiple forwarding tables for for purposes of traffic engineering / policy based routing, with a single firewall instance used as a classifier. vimage-style network stack virtualization provides for more strict isolation on both port and IP address space, independent firewall instances, IPSEC config / state etc., and as such might be better suited for providing enhanced jail-style virtual hosting environments, as well as for providing virtual router "slices". So once we get Julian's multi-FIB stuff in the base system, I see no reason why we couldn't have this functionality replicated in each "vimage" instance, i.e. have multiple independent virtual networking environnments, each with multiple FIBs. Implementationwise, my hacks currently rely on macros for conditional virtualization of global variables / structs. As long as Julian's changes continue to be unconditional, i.e. without playing a similar macroization game, I think integrating this code (once it hits HEAD) into p4/projects/vimage should be more or less a straightforward job. Marko
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