specifying scopid's for link-local IPv6 addrs
Subsystems (2)
Folks -
People running netperf have reported that they have trouble with IPv6 under Linux. Specifically, wereas the use of link-local IPv6 addresses "just works" in netperf under a number of "other OSes" they do not under Linux. I'm ass-u-me-ing 2.6 here, but not sure exactly which ones - I've seen it on a 2.6.18-based RHEL5.
Some poking about and conversation has suggested that one has to set a sin6_scope_id in the sockaddr_in6. This needs to be an index of one of the interfaces in the system, which I presume means walking some additional structures.
Is this a requirement which might be expected to remain in the future, or is it something which might just go away? That will have an effect on netperf future development.
thanks,
rick jones
Quoted 12 lines · Rick Jones
Folks -
People running netperf have reported that they have trouble with IPv6 under Linux. Specifically, wereas the use of link-local IPv6 addresses "just works" in netperf under a number of "other OSes" they do not under Linux. I'm ass-u-me-ing 2.6 here, but not sure exactly which ones - I've seen it on a 2.6.18-based RHEL5.
Some poking about and conversation has suggested that one has to set a
sin6_scope_idin thesockaddr_in6. This needs to be an index of one of the interfaces in the system, which I presume means walking some additional structures.
Quoted 7 lines
Is this a requirement which might be expected to remain in the future, or is it something which might just go away? That will have an effect on netperf future development.
thanks,
rick jones
Rick,
I don't see any way around this. For example, on one of my test systems, I have the following link local routes:
chance% netstat -A inet6 -rn | grep fe80::/64
fe80::/64 :: U 256 0 0 eth0 fe80::/64 :: U 256 0 0 eth2 fe80::/64 :: U 256 0 0 eth3 fe80::/64 :: U 256 0 0 eth4 fe80::/64 :: U 256 0 0 eth5 fe80::/64 :: U 256 0 0 eth6
So if I want to run a link local test to fe80::202:b3ff:fed4:cd1, the system has no way to choose which is the correct interface to use for the test, and will give an error if the interface isn't specified. Here's an example of this with nuttcp:
chance% nuttcp -P5100 fe80::202:b3ff:fed4:cd1
nuttcp-t: Info: attempting to switch to deprecated "classic" mode
nuttcp-t: Info: will use less reliable transmitter side statistics
nuttcp-t: v5.5.5: Error: connect: Invalid argument errno=22
You must explicitly specify the desired interface. For example, on my test system, the correct interface is eth6 which is interface 8 (lo eth0 eth1 eth2 ... eth5 eth6). Here is an example nuttcp test specifying interface 8:
chance% nuttcp -P5100 fe80::202:b3ff:fed4:cd1%8
1178.5809 MB / 10.02 sec = 986.2728 Mbps 12 %TX 15 %RX
nuttcp uses getaddrinfo() which parses the "%<ifindex>" field, and then copies the sin6_scope_id from the res structure to the server's sockaddr_in6 structure before initiating the connect().
-Bill
Quoted 13 lines
Rick,
I don't see any way around this. For example, on one of my test systems, I have the following link local routes:
chance% netstat -A inet6 -rn | grep fe80::/64
fe80::/64 :: U 256 0 0 eth0 fe80::/64 :: U 256 0 0 eth2 fe80::/64 :: U 256 0 0 eth3 fe80::/64 :: U 256 0 0 eth4 fe80::/64 :: U 256 0 0 eth5 fe80::/64 :: U 256 0 0 eth6
Quoted 4 lines
So if I want to run a link local test to fe80::202:b3ff:fed4:cd1, the system has no way to choose which is the correct interface to use for the test, and will give an error if the interface isn't specified.
Yeah, I was wondering about that. I'm not sure if the attempts on "those other OSes" happened to involve multiple interfaces or not. Even so, it "feels" unpleasant for an application to deal with and I wonder if there is a way for a stack to deal with it on the application's behalf. I guess that might involve some sort of layer violation between neightbor discovery and routing (typing while I think about things I know little about...)
Is there RFC chapter and verse I might read about routing with multiple link-local's on a system?
Quoted 11 lines
You must explicitly specify the desired interface. For example, on my test system, the correct interface is eth6 which is interface 8 (lo eth0 eth1 eth2 ... eth5 eth6). Here is an example nuttcp test specifying interface 8:
chance% nuttcp -P5100 fe80::202:b3ff:fed4:cd1%8
1178.5809 MB / 10.02 sec = 986.2728 Mbps 12 %TX 15 %RXnuttcp uses
getaddrinfo()which parses the "%<ifindex>" field, and then copies thesin6_scope_idfrom the res structure to the server'ssockaddr_in6structure before initiating theconnect().
OK, I'll give that a quick try with netperf:
[root@hpcpc106 ~]# netperf -H 192.168.2.107 -c -C -i 30,3 -- -s 1M -S 1M -m 64K -H fe80::207:43ff:fe05:9d%2
TCP STREAM TEST from ::0 (::) port 0 AF_INET6 to fe80::207:43ff:fe05:9d%2 (fe80::207:43ff:fe05:9d) port 0 AF_INET6 : +/-2.5% @ 99% conf.
Cool - it establishes the data connection just fine.
To further demonstrate my ignorance :) is that %n suffix something one might expect in most/all getaddrinfo()'s or is that unique to the one in Linux?
rick jones
Quoted 36 lines · Rick Jones
Quoted 13 lines
Rick,
I don't see any way around this. For example, on one of my test systems, I have the following link local routes:
chance% netstat -A inet6 -rn | grep fe80::/64
fe80::/64 :: U 256 0 0 eth0 fe80::/64 :: U 256 0 0 eth2 fe80::/64 :: U 256 0 0 eth3 fe80::/64 :: U 256 0 0 eth4 fe80::/64 :: U 256 0 0 eth5 fe80::/64 :: U 256 0 0 eth6Quoted 4 lines
So if I want to run a link local test to fe80::202:b3ff:fed4:cd1, the system has no way to choose which is the correct interface to use for the test, and will give an error if the interface isn't specified.
Yeah, I was wondering about that. I'm not sure if the attempts on "those other OSes" happened to involve multiple interfaces or not. Even so, it "feels" unpleasant for an application to deal with and I wonder if there is a way for a stack to deal with it on the application's behalf. I guess that might involve some sort of layer violation between neightbor discovery and routing (typing while I think about things I know little about...)
Is there RFC chapter and verse I might read about routing with multiple link-local's on a system?
Quoted 8 lines
You must explicitly specify the desired interface. For example, on my test system, the correct interface is eth6 which is interface 8 (lo eth0 eth1 eth2 ... eth5 eth6). Here is an example nuttcp test specifying interface 8:
chance% nuttcp -P5100 fe80::202:b3ff:fed4:cd1%8
1178.5809 MB / 10.02 sec = 986.2728 Mbps 12 %TX 15 %RX
Quoted 8 lines
Quoted 3 lines
nuttcp uses
getaddrinfo()which parses the "%<ifindex>" field, and then copies thesin6_scope_idfrom the res structure to the server'ssockaddr_in6structure before initiating theconnect().OK, I'll give that a quick try with netperf:
[root@hpcpc106 ~]# netperf -H 192.168.2.107 -c -C -i 30,3 -- -s 1M -S 1M -m 64K -H fe80::207:43ff:fe05:9d%2
We can even specify the interface name instead of the interface index
<link-local>%ethX
getaddrinfo() uses if_nametoindex() internally to get the index.
Thanks
Sridhar
Quoted 14 lines
TCP STREAM TEST from ::0 (::) port 0
AF_INET6to fe80::207:43ff:fe05:9d%2 (fe80::207:43ff:fe05:9d) port 0AF_INET6: +/-2.5% @ 99% conf.Cool - it establishes the data connection just fine.
To further demonstrate my ignorance :) is that %n suffix something one might expect in most/all getaddrinfo()'s or is that unique to the one in Linux?
rick jones
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Quoted 46 lines · Sridhar Samudrala
Quoted 36 lines · Rick Jones
Quoted 13 lines
Rick,
I don't see any way around this. For example, on one of my test systems, I have the following link local routes:
chance% netstat -A inet6 -rn | grep fe80::/64
fe80::/64 :: U 256 0 0 eth0 fe80::/64 :: U 256 0 0 eth2 fe80::/64 :: U 256 0 0 eth3 fe80::/64 :: U 256 0 0 eth4 fe80::/64 :: U 256 0 0 eth5 fe80::/64 :: U 256 0 0 eth6Quoted 4 lines
So if I want to run a link local test to fe80::202:b3ff:fed4:cd1, the system has no way to choose which is the correct interface to use for the test, and will give an error if the interface isn't specified.
Yeah, I was wondering about that. I'm not sure if the attempts on "those other OSes" happened to involve multiple interfaces or not. Even so, it "feels" unpleasant for an application to deal with and I wonder if there is a way for a stack to deal with it on the application's behalf. I guess that might involve some sort of layer violation between neightbor discovery and routing (typing while I think about things I know little about...)
Is there RFC chapter and verse I might read about routing with multiple link-local's on a system?
Quoted 8 lines
You must explicitly specify the desired interface. For example, on my test system, the correct interface is eth6 which is interface 8 (lo eth0 eth1 eth2 ... eth5 eth6). Here is an example nuttcp test specifying interface 8:
chance% nuttcp -P5100 fe80::202:b3ff:fed4:cd1%8
1178.5809 MB / 10.02 sec = 986.2728 Mbps 12 %TX 15 %RXQuoted 8 lines
Quoted 3 lines
nuttcp uses
getaddrinfo()which parses the "%<ifindex>" field, and then copies thesin6_scope_idfrom the res structure to the server'ssockaddr_in6structure before initiating theconnect().OK, I'll give that a quick try with netperf:
[root@hpcpc106 ~]# netperf -H 192.168.2.107 -c -C -i 30,3 -- -s 1M -S 1M -m 64K -H fe80::207:43ff:fe05:9d%2
Quoted 7 lines
We can even specify the interface name instead of the interface index
<link-local>%ethX
getaddrinfo()usesif_nametoindex()internally to get the index.Thanks
Sridhar
Cool! That's much easier and works great. :-)
chance% nuttcp -P5100 fe80::202:b3ff:fed4:cd1%eth6
1178.5468 MB / 10.02 sec = 986.3239 Mbps 13 %TX 15 %RX
Still learn something new every day. Now if I just could remember it all when I needed it later. :-)
-Thanks
-Bill
Quoted 14 lines
Quoted 6 lines
You must explicitly specify the desired interface. For example, on my test system, the correct interface is eth6 which is interface 8 (lo eth0 eth1 eth2 ... eth5 eth6). Here is an example nuttcp test specifying interface 8:
Quoted 6 lines
chance% nuttcp -P5100 fe80::202:b3ff:fed4:cd1%8
1178.5809 MB / 10.02 sec = 986.2728 Mbps 12 %TX 15 %RXnuttcp uses
getaddrinfo()which parses the "%<ifindex>" field, and then copies thesin6_scope_idfrom the res structure to the server'ssockaddr_in6structure before initiating theconnect().
Quoted 8 lines
OK, I'll give that a quick try with netperf:
[root@hpcpc106 ~]# netperf -H 192.168.2.107 -c -C -i 30,3 -- -s 1M -S 1M
-m 64K -H fe80::207:43ff:fe05:9d%2
TCP STREAM TEST from ::0 (::) port 0AF_INET6to fe80::207:43ff:fe05:9d%2 (fe80::207:43ff:fe05:9d) port 0AF_INET6:
+/-2.5% @ 99% conf.Cool - it establishes the data connection just fine.
Well, I spoke too soon - while it got me past my EINVAL, the connection establishement timed-out. Either I picked the wrong value for n, or I may yet need to make some tweaks to netperf.
rick jones
Quoted 19 lines · Rick Jones
Quoted 19 lines
Rick,
I don't see any way around this. For example, on one of my test systems, I have the following link local routes:
chance% netstat -A inet6 -rn | grep fe80::/64
fe80::/64
:: U 256 0 0 eth0
fe80::/64
:: U 256 0 0 eth2
fe80::/64
:: U 256 0 0 eth3
fe80::/64
:: U 256 0 0 eth4
fe80::/64
:: U 256 0 0 eth5
fe80::/64
:: U 256 0 0 eth6
Quoted 7 lines
Quoted 4 lines
So if I want to run a link local test to fe80::202:b3ff:fed4:cd1, the system has no way to choose which is the correct interface to use for the test, and will give an error if the interface isn't specified.
Yeah, I was wondering about that. I'm not sure if the attempts on "those other OSes" happened to involve multiple interfaces or not.
Yes, there have been attempts. BSD has a concept of default interface.
The default interface is used when the user did not specify the interface/ scope_id.
Other OSs do different things. For example, Tru64 (to pick on a dead system) would try to find the right interface base on the preferences you could set up.
But, in the end the whole thing is really utterly broken since no-one has truly implemented scoped address architecture for link-local addresses. The concept of the link is so closely tied to the 'interface' that I don't know anyone who has separated the two.
Quoted 9 lines
Even
so, it "feels" unpleasant for an application to deal with and I wonder if there is a way for a stack to deal with it on the application's behalf. I guess that might involve some sort of layer violation between neightbor discovery and routing (typing while I think about things I know little about...)Is there RFC chapter and verse I might read about routing with multiple link-local's on a system?
See RFC 4007 for the concepts.
Quoted 21 lines
Quoted 6 lines
You must explicitly specify the desired interface. For example, on my test system, the correct interface is eth6 which is interface 8 (lo eth0 eth1 eth2 ... eth5 eth6). Here is an example nuttcp test specifying interface 8:
Quoted 6 lines
chance% nuttcp -P5100 fe80::202:b3ff:fed4:cd1%8
1178.5809 MB / 10.02 sec = 986.2728 Mbps 12 %TX 15 %RXnuttcp uses
getaddrinfo()which parses the "%<ifindex>" field, and then copies thesin6_scope_idfrom the res structure to the server'ssockaddr_in6structure before initiating theconnect().OK, I'll give that a quick try with netperf:
[root@hpcpc106 ~]# netperf -H 192.168.2.107 -c -C -i 30,3 -- -s 1M -S 1M -m 64K -H fe80::207:43ff:fe05:9d%2
TCP STREAM TEST from ::0 (::) port 0AF_INET6to fe80::207:43ff:fe05:9d%2 (fe80::207:43ff:fe05:9d) port 0AF_INET6:
+/-2.5% @ 99% conf.
Quoted 6 lines
Cool - it establishes the data connection just fine.
To further demonstrate my ignorance :) is that %n suffix something one might expect in most/all getaddrinfo()'s or is that unique to the one in Linux?
This is becoming more generic. I believe HP-UX supports it (if the don't you should kick them :).
-vlad