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Author Topic: Question about routing header  (Read 2040 times)

kasperd

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Question about routing header
« on: November 13, 2012, 01:37:26 PM »

RFC 4620 states:
Quote
   If, while processing a received packet, a node encounters a Routing
   header with an unrecognized Routing Type value, the required behavior
   of the node depends on the value of the Segments Left field, as
   follows:

      If Segments Left is zero, the node must ignore the Routing header
      and proceed to process the next header in the packet, whose type
      is identified by the Next Header field in the Routing header.

      If Segments Left is non-zero, the node must discard the packet and
      send an ICMP Parameter Problem, Code 0, message to the packet's
      Source Address, pointing to the unrecognized Routing Type.
Is this supposed to apply even to if the router currently processing the packet isn't the node in the destination IPv6 address? I have a problem where I am sending packets with routing headers, and I know the node whose IPv6 address is in the destination field is capable of handling this routing header. But the packet never reaches the destination. I also don't see any ICMP errors indicating what happened.

Are there any routers known to silently drop packets with routing headers they don't understand, even when they are not the destination of the packet, and were just supposed to forward it?
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kasperd

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Re: Question about routing header
« Reply #1 on: November 13, 2012, 02:57:09 PM »

Turns out it wasn't actually the segments left that caused the problem. Using a modified traceroute I was able to track down both on which hop the packets are silently dropped, and what the criteria is.

It turns out that if the end of the routing header is within the first 256 bytes of the payload, then the packet makes it through. If the end of the routing header is beyond the first 256 bytes of the payload, the packet is silently dropped. The packet size and segments left value didn't affect the outcome.
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