Date: Tue, 19 Aug 2014 20:06:38 +0400 From: Dmitry Selivanov <sd@rlan.ru> To: "Alexander V. Chernikov" <melifaro@FreeBSD.org> Cc: freebsd-ipfw <freebsd-ipfw@freebsd.org>, "freebsd-net@freebsd.org" <freebsd-net@freebsd.org> Subject: Re: ipfw named objejcts, table values and syntax change Message-ID: <53F3760E.9070206@rlan.ru> In-Reply-To: <53F3563D.6020107@FreeBSD.org> References: <53DC01DE.3000000@FreeBSD.org> <CA%2BhQ2%2BgNjA0rucTYAaPYQKtEMt9GZLC6RCi%2BOgPVRpuDC5Ei7Q@mail.gmail.com> <53DCA25C.1000108@FreeBSD.org> <53DF55FA.8010303@FreeBSD.org> <20140804115817.GA13814@onelab2.iet.unipi.it> <53DFE438.5050209@FreeBSD.org> <53E4BE62.4050303@rlan.ru> <53EE0A30.4020800@FreeBSD.org> <53EE16DE.9020209@rlan.ru> <53EE252D.10109@FreeBSD.org> <53F3563D.6020107@FreeBSD.org>
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19.08.2014 17:50, Alexander V. Chernikov пишет:
> On 15.08.2014 19:20, Alexander V. Chernikov wrote:
>> On 15.08.2014 18:19, Dmitry Selivanov wrote:
>>> 15.08.2014 17:25, Alexander V. Chernikov пишет:
>>>> On 08.08.2014 16:11, Dmitry Selivanov wrote:
>>>>> 04.08.2014 23:51, Alexander V. Chernikov пишет:
>>>>>> On 04.08.2014 15:58, Luigi Rizzo wrote:
>>>>>>> On Mon, Aug 04, 2014 at 01:44:26PM +0400, Alexander V. Chernikov wrote:
>>>>>>>> On 02.08.2014 12:33, Alexander V. Chernikov wrote:
>>>>>>>>> On 02.08.2014 10:33, Luigi Rizzo wrote:
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> On Fri, Aug 1, 2014 at 11:08 PM, Alexander V. Chernikov
>>>>>>>>>> <melifaro@freebsd.org <mailto:melifaro@freebsd.org>> wrote:
>>>>>>>>>>
>>>>>>>>>> Hello all.
>>>>>>>>>>
>>>>>>>>>> I'm currently working on to enhance ipfw in some areas.
>>>>>>>>>> The most notable (and user-visible) change is named table support.
>>>>>>>>>> The other one is support for different lookup algorithms for different
>>>>>>>>>> key types.
>>>>>>>>>>
>>>>>>>>>> For example, new ipfw permits writing this:
>>>>>>>>>>
>>>>>>>>>> ipfw table tb1 create type cidr
>>>>>>>>>> ipfw add allow ip from table(tl1) to any
>>>>>>>>>> ipfw add allow ip from any lookup dst-ip tb1
>>>>>>>>>>
>>>>>>>>>> ipfw table if1 create type iface
>>>>>>>>>> ipfw add skipto tablearg ip from any to any via table(if1)
>>>>>>>>>>
>>>>>>>>>> or even this:
>>>>>>>>>> ipfw table fl1 create type flow:src-ip,proto,dst-ip,dst-port
>>>>>>>>>> ipfw table fl1 add 10.0.0.5,tcp,10.0.0.6,80 4444
>>>>>>>>>> ipfw add allow ip from any to any flow table(fl1)
>>>>>>>>>>
>>>>>>>>>> all these changes fully preserve backward compatibility.
>>>>>>>>>> (actually tables needs now to be created before use and their type needs
>>>>>>>>>> to match with opcode used, but new ipfw(8) performs auto-creation
>>>>>>>>>> for cidr tables).
>>>>>>>>>>
>>>>>>>>>> There is another thing I'm going to change and I'm not sure I can keep
>>>>>>>>>> the same compatibility level.
>>>>>>>>>>
>>>>>>>>>> Table values, from one point of view, can be classified to the following
>>>>>>>>>> types:
>>>>>>>>>>
>>>>>>>>>> - skipto argument
>>>>>>>>>> - fwd argument (*)
>>>>>>>>>> - link to another object (nat, pipe, queue)
>>>>>>>>>> - plain u32 (not bound to any object)
>>>>>>>>>> (divert/tee,netgraph,tag/utag,limit)
>>>>>>>>>>
>>>>>>>>>> There are the following reasons why I think it is necessary to implement
>>>>>>>>>> explicit table values typing (like tables):
>>>>>>>>>> - Implementing fwd tablearg for IPv6 hosts requires indirection table
>>>>>>>>>> - Converting nat/pipe instance ids to names renders values unusable
>>>>>>>>>> - retiring old hack with storing saved pointer of found object/rule
>>>>>>>>>> inside rule w/o proper locking
>>>>>>>>>> - making faster skipto
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> ??????i don't buy the idea that you need typed arguments
>>>>>>>>>> for all the cases above. Maybe the case that
>>>>>>>>>> may make sense is the fwd argument (and in the future
>>>>>>>>>> something else).
>>>>>>>>>> We already discussed, i think, the fact that now it
>>>>>>>>>> is legal to have references to non existing things
>>>>>>>>>> (skipto, pipes etc.) implemented as u32.
>>>>>>>>>> Removing that would break configurations.
>>>>>>>>> It depends on actual implementation. This can be preserved by
>>>>>>>>> auto-creating necessary objects in kernel and/or in userspace, so
>>>>>>>>> we can (and should) avoid breaking in this particular way.
>>>>>>>> Can you please explain your vision on values another time?
>>>>>>>> As far as I understand, you're not against it in general, but the
>>>>>>>> details matter:
>>>>>>>> * IP address can be one of the types (it won't break much, and we can
>>>>>>>> simply skip that one for MFC)
>>>>>>>> * what about typing for nat/pipes ? we're not going to convert their ids
>>>>>>>> to names? (or maybe you can suggest other non-disruptive way?)
>>>>>>>> * everything else is type "u32"
>>>>>>>
>>>>>>> Correct, I am mostly concerned about the details, not on the general concept.
>>>>>>>
>>>>>>> To summarize the discussion Alexander and I had about converting
>>>>>>> identifiers from numbers to arbitrary strings (this is partly related
>>>>>>> to the values stored in tables, but I think we should have a coherent
>>>>>>> behaviour)
>>>>>>>
>>>>>>> 1. CURRENTLY ipfw uses numeric identifiers in a small range (16 bits or less)
>>>>>>> for rules, pipes, queues, tables, probably nat instances.
>>>>>>>
>>>>>>> 2. CURRENTLY, in all the above contexts, it is legal to reference a
>>>>>>> non existing object (rule, pipe, table names, etc.),
>>>>>>> and the kernel will do something reasonable, namely jump to the
>>>>>>> next rule, drop traffic for non existing pipes, and so on.
>>>>>>>
>>>>>>> 3. of course we want to preserve backward compatibility both for
>>>>>>> the ioctl interface, and for user configurations.
>>>>>>>
>>>>>>> 4. The in-kernel representation of identifiers is not visible to users,
>>>>>>> so we can use a numeric representation in the kernel for identifiers.
>>>>>>> Strings like "12345" are converted with atoi() or the like,
>>>>>>> whereas for other identifiers or numbers outside of the 2^16 range
>>>>>>> the kernel manages a translation table, allocating new numeric
>>>>>>> identifiers if a new string appears.
>>>>>>> This permits backward compatibility for old rulesets, and does not
>>>>>>> impact performance because the translation table is only
>>>>>>> used during rules additions or deletion.
>>>>>> Yes. However this requires either holding either (1) 2 pointers (old&new
>>>>>> arrays), or (2) 65k+ index array, or (3) chained hash table.
>>>>>> (1) would require additional pointers for each subsystem (and some
>>>>>> additional management),
>>>>>> (2) will definitely upset embedded guys and
>>>>>> (3) is worse in terms of performance
>>>>>>>
>>>>>>> With this in mind, i think we should follow a similar approach for
>>>>>>> objects stored in tables, hence
>>>>>>>
>>>>>>> if an u32 value was available in the past, it must be
>>>>>>> available also in the new implementation.
>>>>>>>
>>>>>>> The issue with tables is that some convoluted configuration could
>>>>>>> use the same table to reference pipes _and_ rules _and_ perhaps
>>>>>>> other things represented as numbers (the former is not too strange,
>>>>>>> if i have a large configuration i might place sections at rules
>>>>>>> 12000, 13000, 14000... and associate pipes with the same numberic
>>>>>>> identifier to each block of rules).
>>>>>>>
>>>>>>> Typed table values would clearly disturb backward compatibility
>>>>>>> in the above configurations. However it should not be difficult
>>>>>>> to accept arbitrary strings as the values stored in tables, and
>>>>>>> then store multiple representations as appropriate, including:
>>>>>> Well, I've thought about thas one. It may be an option, but the details
>>>>>> are not so promising (below)
>>>>>>> - the string representation, unconditionally
>>>>>>> - for names that can be resolved by DNS, the ipv6 and ipv4 address(es)
>>>>>>> associated with them. ipfw already translates hostnames in rules
>>>>>>> so this is POLA
>>>>>> I'm not happy what ipfw(8) is doing instead of translation. The proper
>>>>>> way would be not simply using first AF_INET answer but saving ALL
>>>>>> IPv4+IPv6 records inside rule (and some more tracking should be done
>>>>>> afterwards, but that's totally different story). Additionally, I'm
>>>>>> unsure if we really need next-hop value expressed as hostname (how can
>>>>>> we deal with multiple addresses and diffrent AFs?). We may store strings
>>>>>> (and I think we should do it) but I'm unsure about this particular
>>>>>> option of interpreting them.
>>>>>>> - for other strings, a u32 from the translation table as previously
>>>>>>> indicated
>>>>>>> - and for numeric values, the u32 representation (truncated if needed,
>>>>>>> according to whatever is the existing behaviour)
>>>>>>> - <add other representations if needed>
>>>>>>> If we cannot generate an u32 we will put some value (e.g. 0)
>>>>>>> that hopefully will not cause confusion.
>>>>>> As far as I understand, we accept some string "s" as table value inside
>>>>>> the kernel, than, we have some logic that says:
>>>>>> oh, dummynet pipe has the same name "s"s, oh, nat entity with name "s"
>>>>>> has just been created, let's save indices.
>>>>>>
>>>>>> That would require additional indirection table like:
>>>>>>
>>>>>> index | [ skipto idx | nat idx | pipe idx | queue idx | fwd index ]
>>>>>> ( so we will have 2-level indirection table for fwd if we do IPv6)
>>>>>>
>>>>>> We can optimize this if we use "same name -> same kidx" approach
>>>>>> regardless of kernel object we're refering to. That might require some
>>>>>> more memory, but that's OK from my point of view.
>>>>>>
>>>>>> So we end up with
>>>>>> int [ skipto idx | fwd idx | obj idx ]
>>>>>>
>>>>>> idx "0" is special value which means the same as 2.CURRENT
>>>>>>
>>>>>> That looks better, but still way to complex.
>>>>>> I do care about compatibility, but it's hard to improve things without
>>>>>> changing.
>>>>>>
>>>>>> I'd like to propose the following:
>>>>>> * Split values into 3 types ("ip|nexthop", "number", "object")
>>>>>> * Do not insist on object existence, use value "0" to mimic 2.CURRENT
>>>>>> behavior.
>>>>>> * Retain full compatibility by introducing special value type "legacy"
>>>>>> which matches any type and is backed by given indirection table.
>>>>>> * Issue warning in ipfw(8) binary on all auto-created tables that
>>>>>> auto-creation is legacy and this behavior will be dropped in next major
>>>>>> release (e.g. 11.0)
>>>>>> * Save this behavior in MFC but drop "legacy" tables in head after a
>>>>>> month after actual MFC.
>>>>>>
>>>>>> That do you think?
>>>>>>>
>>>>>>> If we do it this way, we should be able to preserve backward
>>>>>>> compatibility _and_ add features that people may need.
>>>>>>>
>>>>>>> cheers
>>>>>>> luigi
>>>>>>>
>>>>> Here is my idea: tablearg should contain more than one value. I think getting several values from one table lookup is faster than several table lookups with one value.
>>>>> Let tablearg be not just uint32, but array with different value types inside it.
>>>> There are some use cases where we might need 2-level value lookup (e.g. algo returning index for index table where actual data reside) and each data item can
>>>> really be up to 64-bytes long. The problem is in actual partitioning and compatibility.
>>>>>
>>>>> For example I have many such rules:
>>>>> allow src-ip 1.2.3.4 MAC any 11:22:33:44:55:66 recv vlan1234 dst-ip 1.1.1.1
>>>> Sorry, what task are you solving by using given rules?
>>> Small ISP, clients have static IP with MAC-authorization. Src iface must be checked to prevent IP-spoofing. Dst-IP sometimes is used for p2p-channels.
>>>>>
>>>>> These rules can be replaced with such construction:
>>>>> allow src-ip table(1) MAC any tablearg[1] recv tablearg[2] dst-ip tablearg[3]
>>>>>
>>>>> But I don't think indexing by value is a good idea. I think index==starting byte is a better way:
>>>>> allow src-ip table(1) MAC any tablearg:0 recv tablearg:6 dst-ip tablearg:32
>>>>> where MAC's 6 bytes are from 0 to 5 in tablearg; iface string is from 6 and till \0, but less than 26 bytes; and IPv4's 4 bytes are from 32 to 35.
>>>>
>>>>> So we need to create table for it:
>>>>> table 1 set MAC:0 string:6:26 ip:32
>>>>> table 1 add 1.2.3.4 11:22:33:44:55:66 vlan1234 1.1.1.1
>>>>>
>>>>> String can be used both for iface and comment.
>>>>> Other possible value types:
>>>>> uint16 for nat, pipe, skipto and other 2-bytes actions
>>>>> IPv4 4 bytes
>>>>> CIDRv4 5 bytes
>>>>> IPv6 16 bytes
>>>>> CIDRv6 17 bytes
>>>>> table_id 2 bytes - link to another table
>>>> Well, it seems we have enough space to store most of these, however, problems seem to remain the same: typing and compatibility.
>>>> When you're creating new table (or it is auto-created) which values types should be assumed ? All of them?
>>> Default - as usually uint32.
>> I can't see "uint32" value in the list you have specified before. I'll rephrase:
>> what value types (from the list above or similar) should ipfw(8) or kernel fill in case of "default" table?
>> (And once again, what should we print as value) ?
>> Please think about
>> a) old ipfw binaries
>> b) new ipfw binaries using exactly the same ruleset they are already using (with, for example, both "skipto tablearg" and "fwd tablearg " tables).
At that time I meant default table "header" is "ip:0" (in my context). It would be completely compatible with old ipfw tables.
> I've increased kernel<>userland 'struct tentry' value field to 64 bytes.
> It looks like we were talking about a bit different things.
> Let me try to explain the problem I'm stuck with:
>
> We may take the road you've suggested, it looks OK:
>
> * by default tables are created with "all-values" mask.
> * ipfw(8) value treats default "ipfw table X add Y val" input where value is u32 number as input data for each type specified in all-values without returning error
> * for non-default mask value data should be validated.
>
> e.g. if we have table with valtype="skipto,nat,pipe,ip4,ip6" and "100" as input -> it turns to "100,100,0.0.0.0,::".
I don't fully understand. One "100" value for all valtypes? Then "100" can't be equal "0.0.0.0" and "::". Or you meant "100,100,0,0" as input?
> If we have value with valtype="skipto,ip6" and "100" as input -> error while the valid one would be "100,2a01::1:111", for example.
>
> I'm unsure how should one be able to update _specific_ value (e.g. update nat id or skipto arg), but that's not the problem.
Maybe new command would help, like "ipfw table X set Y newval".
>
> The problem arises if we start talking about using names for nat/pipe/queue ids instead of numbers.
> If we have nat instances "nat1", "11" and "23", and one specifies "44" as part of value, logic starts to be complex:
>
> we either require nat "44" to exists (and I'm unsure if we can auto-create it *) or start doing complex stuff like tracking all those non-existing objects:
> e.g. add some special record somewhere that we're wating for nat instance "44" to be created, than auto-update given value with its kernel index,
> than, do something reasonable if nat "44" instance is destroyed (OK, nat instance can't be destroyed, but pipe can).
> .. and we have to do the same for pipes/queues and any following kernel object.
>
> Or we have to require user to reference existing objects only (create explicitly before use). This one makes things easier in code, but require user to change their scripts.
> It looks like there is no consensus on that point.
User can destroy object after table creating. I think this way: "no object - no packet (explicitly deny)". No need to check object existence.
>
> * Maybe auto-creation is not so tricky and we should try to evaluate it..
>
>>
>>
>>>> What should `ipfw table X list` show as "value" field ?
>>> I added table "header" in this line:
>>> table 1 set MAC:0 string:6:26 ip:32
>> I don't think that user should be able to set any offsets in userland. Exact offsets of variable of given type needs to be enforced by kernel,
>> so you may fill that you want "mac" and "ip" as values for given table, but not lengths or offsets.
Does your way allow to use strings (e.g. iface or comments)?
>>> So `ipfw table X list` should show something like this:
>>> ---table(0)---
>>> 1.2.3.4/32 11:22:33:44:55:66 vlan1234 1.1.1.1
>>> We can also add "header" description in output (with or without additional parameter - depends on compatibility needs) like this:
>>> ---table(0)--- addr MAC iface IPv4
>>>> How should ipfw(8) treat "add 1.1.1.1 0" input?
>>> It should look at table "header" and return error message like "Value doesn't match table header"
>>
>>>> What will happen if we want to add another type field to this list? (MAC address of Infiniband MAC address, for example).
>>> I don't think there is a sense to mix both MAC[6] and MAC[20] values in 1 table. It is easier to create 2 tables with different "headers".
>>> For Infiniband we can add another type: MAC20 (or something like this). Or we can use "MAC"-type like string type(see above): MAC:6:25 (1st and last bytes, or 1st and length).
>>>>
>>>>>
>>>>> Table value length can be set for example with loader tunable like net.inet.ip.fw.table_value_length.
>>>>> Even with default uint32 value length we can get 2 uint16 values or 4 uint8 values, this can help in some configurations.
>>>>>
>>>>> This way is more complex, but much more flexible. It's like netgraph subsystem.
>>>>> I think it suites both Alexander and Luigi requests.
>>>>>
>>>>>
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