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author | YOSHIFUJI Hideaki / 吉藤英明 <yoshfuji@linux-ipv6.org> | 2013-03-25 08:26:08 +0000 |
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committer | David S. Miller <davem@davemloft.net> | 2013-03-26 12:32:13 -0400 |
commit | 61a7839a19c157d11930fe69697a4c90884bf7c4 (patch) | |
tree | ef2dd78384873146897c376a85f283a57bd90637 /net/ipv4 | |
parent | 382c4b4090b7394d079c199ba053a378c6cd45b8 (diff) | |
download | op-kernel-dev-61a7839a19c157d11930fe69697a4c90884bf7c4.zip op-kernel-dev-61a7839a19c157d11930fe69697a4c90884bf7c4.tar.gz |
firewire net: Ignore spd and max_payload advertised by ARP.
Stefan Richter <stefanr@s5r6.in-berlin.de> says:
| As far as I can tell, it would be best to ignore max_rec and sspd from ARP
| and NDP but keep using the respective information from firewire-core
| instead (handed over by fwnet_probe()).
|
| Why? As I noted earlier, RFC 2734:1999 and RFC 3146:2001 were apparently
| written with a too simplistic notion of IEEE 1394 bus topology, resulting
| in max_rec and sspd in ARP-1394 and NDP-1394 to be useless, IMO.
|
| Consider a bus like this:
|
| A ---- B ==== C
|
| A, B, C are all IP-over-1394 capable nodes. ---- is an S400 cable hop,
| and ==== is an S800 cable hop.
|
| In case of unicasts or multicasts in which node A is involved as
| transmitter or receiver, as well as in case of broadcasts, the speeds
| S100, S200, S400 work and speed S400 is optimal.
|
| In case of anything else, IOW in case of unicasts or multicasts in which
| only nodes B and C are involved, the speeds S100, S200, S400, S800 work
| and speed S800 is optimal.
|
| Clearly, node A should indicate sspd = S400 in its ARP or NDP packets.
| But which sspd should nodes B and C set there? Maybe they set S400, which
| would work but would waste half of the available bandwidth in the second
| case. Or maybe they set S800, which is OK in the second case but would
| prohibit any communication with node A if blindly taken for correct.
|
| On the other hand, firewire-core *always* gives us the correct and optimum
| peer-to-peer speed and asynchronous packet payload, no matter how simple
| or complex the bus topology is and no matter in which temporal order nodes
| join the bus and are discovered.
CC: Stefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4')
0 files changed, 0 insertions, 0 deletions