RH_AtHost - check Routing Header Processing (at Host)
Host
1. Reboot Target 2. Send Router Advertisement 3. Wait Neighbor Solicitation (DAD)
Tester Target
| |
|-------------------------->|
| ICMP Echo Request |
| |
|<--------------------------|
| ICMP Echo Reply |
| |
v v
1. Send Echo Request 2. Receive Echo Reply
Network topology
(Link0)
Tester Target
Host1 ------ Router1 ------ Router2 ------ Router3 ------ Host2
Global 6 Global 4 Global 2 Global 0
ICMP Echo Request is:
IPv6 Header
Version = 6
Traffic Class = 0
FlowLabel = 0
PayloadLength = 72
NextHeader = 43 (Routing Header)
SourceAddress = Global 6 Address (Host1)
DestinationAddress = Global 0 Address (Host2)
Routing Header
NextHeader = 58 (ICMP)
HeaderExtLength = 6
RoutingType = 0
SegmentsLeft = 0
Address[1] = Global 6 Address (Router1)
Address[2] = Global 4 Address (Router2)
Address[3] = Global 2 Address (Router3)
ICMP Echo Request
Type = 128 (Echo Request)
PASS: ICMP Echo Reply received
ICMP Echo Reply is:
IPv6 Header
Version = 6
Traffic Class = 0
FlowLabel = 0
PayloadLength = 16
NextHeader = 58 (ICMP)
SourceAddress = Global 0 Address (Host2)
DestinationAddress = Global 6 Address (Host1)
ICMP Echo Reply
Type = 129 (Echo Reply)
RFC2460
4.4 Routing Header
The Routing header is used by an IPv6 source to list one or more intermediate nodes to be "visited" on the way to a packet's destination. This function is very similar to IPv4's Loose Source and Record Route option. The Routing header is identified by a Next Header value of 43 in the immediately preceding header, and has the following format:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Header | Hdr Ext Len | Routing Type | Segments Left |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. type-specific data .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Next Header 8-bit selector. Identifies the type of header
immediately following the Routing header. Uses
the same values as the IPv4 Protocol field
[RFC-1700 et seq.].
Hdr Ext Len 8-bit unsigned integer. Length of the Routing
header in 8-octet units, not including the first
8 octets.
Routing Type 8-bit identifier of a particular Routing header
variant.
Segments Left 8-bit unsigned integer. Number of route
segments remaining, i.e., number of explicitly
listed intermediate nodes still to be visited
before reaching the final destination.
type-specific data Variable-length field, of format determined by
the Routing Type, and of length such that the
complete Routing header is an integer multiple
of 8 octets long.
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.
If, after processing a Routing header of a received packet, an intermediate node determines that the packet is to be forwarded onto a link whose link MTU is less than the size of the packet, the node must discard the packet and send an ICMP Packet Too Big message to the packet's Source Address.
The Type 0 Routing header has the following format:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Header | Hdr Ext Len | Routing Type=0| Segments Left |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Address[1] +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Address[2] +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. . .
. . .
. . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Address[n] +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Next Header 8-bit selector. Identifies the type of header
immediately following the Routing header. Uses
the same values as the IPv4 Protocol field
[RFC-1700 et seq.].
Hdr Ext Len 8-bit unsigned integer. Length of the Routing
header in 8-octet units, not including the first
8 octets. For the Type 0 Routing header, Hdr
Ext Len is equal to two times the number of
addresses in the header.
Routing Type 0.
Segments Left 8-bit unsigned integer. Number of route
segments remaining, i.e., number of explicitly
listed intermediate nodes still to be visited
before reaching the final destination.
Reserved 32-bit reserved field. Initialized to zero for
transmission; ignored on reception.
Address[1..n] Vector of 128-bit addresses, numbered 1 to n.</B>
Multicast addresses must not appear in a Routing header of Type 0, or in the IPv6 Destination Address field of a packet carrying a Routing header of Type 0.
A Routing header is not examined or processed until it reaches the node identified in the Destination Address field of the IPv6 header. In that node, dispatching on the Next Header field of the immediately preceding header causes the Routing header module to be invoked, which, in the case of Routing Type 0, performs the following algorithm:
if Segments Left = 0 {
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 greater than n {
send an ICMP Parameter Problem, Code 0, message to the Source
Address, pointing to the Segments Left field, and discard the
packet
}
else {
decrement Segments Left by 1;
compute i, the index of the next address to be visited in
the address vector, by subtracting Segments Left from n
if Address [i] or the IPv6 Destination Address is multicast {
discard the packet
}
else {
swap the IPv6 Destination Address and Address[i]
if the IPv6 Hop Limit is less than or equal to 1 {
send an ICMP Time Exceeded -- Hop Limit Exceeded in
Transit message to the Source Address and discard the
packet
}
else {
decrement the Hop Limit by 1
resubmit the packet to the IPv6 module for transmission
to the new destination
}
}
}
}
perldoc V6evalTool