why does DCCP SO_REUSEADDR have to be SOL_DCCP?

DISCUSSION Rick Jones 2 participants 4 messages Feb 2, 2008 – Feb 4, 2008

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Rick Jones

author

2008-02-02 01:42 UTC #0 lore raw

Hi -

I'm tweaking the netperf omni tests to be able to run over DCCP. I've run across a not-unorecedented problem with getaddrinfo() not groking either SOCK_DCCP or IPPROTO_DCCP in the hints, and that I can more or less live with - I had to do a kludge for getaddrinfo() for IPPROTO_SCTP under Linux at one point and I can see how the two are not necessarily going to be in sync.

And I've worked-around no user-level include files (ie without setting __KERNEL__) define the DCCP stuff, and that is OK too, albeit somewhat inconvenient.

My question though is why on earth does an SO_REUSEADDR setsockopt() against a DCCP socket have to be SOL_DCCP? SCTP and TCP are quite happy with SOL_SOCKET, and it might be foolish consistency, but since the option _does_ begin with SO_ I'd have expected it to work for SOL_SOCKET, but (again RHEL5.1, yes, I do plan on getting upstream but have to satisfy several masters) it doesn't seem to be the case - a subsequent listen() or connect() call after an SOL_SOCKET SO_REUSEADDR against a DCCP socket leaves one SOL as it were...

Of course the setsockopt(SO_REUSEADDR) against the DCCP socket using SOL_SOCKET itself doesn't fail, only the later listen() or connect() call...

happy benchmarking,

rick jones

Arnaldo Carvalho de Melo

2008-02-02 02:53 UTC #1 lore raw

Em Fri, Feb 01, 2008 at 05:42:23PM -0800, Rick Jones escreveu:

Quoted 8 lines

Hi -
I'm tweaking the netperf omni tests to be able to run over DCCP. I've run across a not-unorecedented problem with getaddrinfo() not groking either SOCK_DCCP or IPPROTO_DCCP in the hints, and that I can more or less live with - I had to do a kludge for getaddrinfo() for IPPROTO_SCTP under Linux at one point and I can see how the two are not necessarily going to be in sync.

See the ttcp patch where we do a xgetaddrinfo crude hack to handle dccp:

http://vger.kernel.org/~acme/dccp/ttcp.c

Quoted 3 lines

And I've worked-around no user-level include files (ie without setting __KERNEL__) define the DCCP stuff, and that is OK too, albeit somewhat inconvenient.

Humm, for what? Again, see the ttcp code above:

Quoted 8 lines

My question though is why on earth does an SO_REUSEADDR setsockopt() against a DCCP socket have to be SOL_DCCP? SCTP and TCP are quite happy with SOL_SOCKET, and it might be foolish consistency, but since the option _does_ begin with SO_ I'd have expected it to work for SOL_SOCKET, but (again RHEL5.1, yes, I do plan on getting upstream but have to satisfy several masters) it doesn't seem to be the case - a subsequent listen() or connect() call after an SOL_SOCKET SO_REUSEADDR against a DCCP socket leaves one SOL as it were...

Strange, lemme check...

1. sys_socketcall ->
2. sys_setsockopt ->
3. if (level == SOL_SOCKET) {
4. sock_setsockopt:
5. case SO_REUSEADDR:
6. sk->sk_reuse = valbool;
7. } else
8. sock->ops->setsockopt = inet_dccp_ops->setsockopt =
9. inet_dccp_ops->setsockopt = sock_common_setsockopt ->
10. sk->sk_prot->setsockopt = dccp_v4_prot->setsockopt =
11. dccp_setsockopt
12. if (level != SOL_DCCP)
13. return inet_csk(sk)->icsk_af_ops->setsockopt() =
14. ip_setsockopt
15. return do_dccp_setsockopt()

SO_REUSEADDR is handled in 4, if you pass SOL_SOCKET.

If instead you pass SOL_DCCP we'll go down the rabbit hole till do_dccp_setsockopt() and SO_REUSEADDR, that is equal to 2, will be interpreted as DCCP_SOCKOPT_SERVICE, that is also equal to 2, so you'll be setting the service, not changing the SO_REUSEADDR setting.

The problem here is that you need to use:

setsockopt(fd, SOL_DCCP, DCCP_SOCKOPT_PACKET_SIZE, service,

           sizeof(service));

Again, take a look at the ttcp patch, the other patches for iperf, netcat, etc handles this.

Quoted 5 lines

Of course the setsockopt(SO_REUSEADDR) against the DCCP socket using SOL_SOCKET itself doesn't fail, only the later listen() or connect() call...
happy benchmarking,

Look forward for a happy DCCP netperf bencharking session!

Thanks a lot,

- Arnaldo

Arnaldo Carvalho de Melo

2008-02-02 03:03 UTC #2 lore raw

Em Sat, Feb 02, 2008 at 12:52:59AM -0200, Arnaldo Carvalho de Melo escreveu:

Quoted 9 lines

If instead you pass SOL_DCCP we'll go down the rabbit hole till do_dccp_setsockopt() and SO_REUSEADDR, that is equal to 2, will be interpreted as DCCP_SOCKOPT_SERVICE, that is also equal to 2, so you'll be setting the service, not changing the SO_REUSEADDR setting.
The problem here is that you need to use:
setsockopt(fd, SOL_DCCP, DCCP_SOCKOPT_PACKET_SIZE, service,
           sizeof(service));

Further info on DCCP service codes:

http://www.rfc.net/rfc4340.txt -> "8.1.2. Service Codes"

Quoted 2 lines

Again, take a look at the ttcp patch, the other patches for iperf, netcat, etc handles this.

- Arnaldo

Rick Jones

author

2008-02-04 18:46 UTC #3 lore raw

In reply to Arnaldo Carvalho de Melo

Quoted 10 lines · Arnaldo Carvalho de Melo

Em Fri, Feb 01, 2008 at 05:42:23PM -0800, Rick Jones escreveu:
Quoted 3 lines
Hi -
I'm tweaking the netperf omni tests to be able to run over DCCP. I've run across a not-unorecedented problem with getaddrinfo() not groking either SOCK_DCCP or IPPROTO_DCCP in the hints, and that I can more or less live with - I had to do a kludge for getaddrinfo() for IPPROTO_SCTP under Linux at one point and I can see how the two are not necessarily going to be in sync.
See the ttcp patch where we do a xgetaddrinfo crude hack to handle dccp:
http://vger.kernel.org/~acme/dccp/ttcp.c

That is basically what netperf ends-up doing presently, although it is much more vocal about it :)

Quoted 4 lines

Quoted 1 line
And I've worked-around no user-level include files (ie without setting __KERNEL__) define the DCCP stuff, and that is OK too, albeit somewhat inconvenient.
Humm, for what? Again, see the ttcp code above:

I see that it too is making a guess for the DCCP defines. I prefer to get those from the "regular" include files because several of them can be platform specific and netperf happens on many platforms. If DCCP is still "experimental" I suppose that living with defines not being in user-level includes is to be expected.

Quoted 21 lines

Quoted 1 line
My question though is why on earth does an SO_REUSEADDR setsockopt() against a DCCP socket have to be SOL_DCCP? SCTP and TCP are quite happy with SOL_SOCKET, and it might be foolish consistency, but since the option _does_ begin with SO_ I'd have expected it to work for SOL_SOCKET, but (again RHEL5.1, yes, I do plan on getting upstream but have to satisfy several masters) it doesn't seem to be the case - a subsequent listen() or connect() call after an SOL_SOCKET SO_REUSEADDR against a DCCP socket leaves one SOL as it were...
Strange, lemme check...
1. sys_socketcall ->
2. sys_setsockopt ->
3. if (level == SOL_SOCKET) {
4. sock_setsockopt:
5. case SO_REUSEADDR:
6. sk->sk_reuse = valbool;
7. } else
8. sock->ops->setsockopt = inet_dccp_ops->setsockopt =
9. inet_dccp_ops->setsockopt = sock_common_setsockopt ->
10. sk->sk_prot->setsockopt = dccp_v4_prot->setsockopt =
11. dccp_setsockopt
12. if (level != SOL_DCCP)
13. return inet_csk(sk)->icsk_af_ops->setsockopt() =
14. ip_setsockopt
15. return do_dccp_setsockopt()

Quoted 6 lines

SO_REUSEADDR is handled in 4, if you pass SOL_SOCKET.
If instead you pass SOL_DCCP we'll go down the rabbit hole till do_dccp_setsockopt() and SO_REUSEADDR, that is equal to 2, will be interpreted as DCCP_SOCKOPT_SERVICE, that is also equal to 2, so you'll be setting the service, not changing the SO_REUSEADDR setting.

That is completely unexpected. Particularly based on the implications of:

http://www.linux-foundation.org/en/Net:DCCP

Quoted 5 lines

The problem here is that you need to use:
setsockopt(fd, SOL_DCCP, DCCP_SOCKOPT_PACKET_SIZE, service,
           sizeof(service));

I guess since I was going off the URL above and it doesn't mention that... :) I was just blythly ass-u-me-ing that DCCP was usable as a "just swap the IPPROTO in your socket() call and go" sort of thing. And wasn't expecting to have to make additional setsockopt() calls.

Quoted 1 line

Look forward for a happy DCCP netperf bencharking session!

Looks like some very basic stuff (whatever one gets passing SOL_DCCP to the SO_REUSEADDR setting) is functioning in the top of trunk. I now have to think about what to do wrt DCCP service types. If I should add something to the parsing of -T dccp or if I should add yet another command-line option :)

happy benchmarking,

rick jones