rfc2765_3.1_hoplimit.seq - Verify IPv6 <-> IPv4 header
translation in accordance with RFC2765 [SIIT]
Router
rfc2765_3.1_hoplimit.seq [-tooloption ...]
-p rfc2765_3.1_hoplimit.def
Before this test starts, run initialize.seq.
This test verifies that NUT properly translates TTL - 1 to
Hop Limit, or sends an ICMPv4 Time Exceeded.
Network Topology
Link0
--------------------------
| |
TN NUT
| |
--------------------------
Link1
TN -- (Link0) -- NUT NUT -- (Link1) -- TN
--------------------- ------------------------
1.1.
<===================
ICMPv4 Echo request
IPv4 Header
src address : TN LINK1 IPv4 address
dst address : TN LINK0 IPv4 address
Don't Fragment = 1
More fragments = 0
Offset = 0
TTL = 255
ICMPv4 echo request
1.2.
<<JUDGMENT>>
<===================
ICMPv6 Echo Request
IPv6 Header
src address : TN LINK1 IPv4 embedded IPv6 address
dst address : TN LINK0 IPv4 embedded IPv6 address
Hop Limit = 254
ICMPv6 echo request
2.1.
<===================
ICMPv4 Echo request
IPv4 Header
src address : TN LINK1 IPv4 address
dst address : TN LINK0 IPv4 address
Don't Fragment = 1
More fragments = 0
Offset = 0
TTL = 64
ICMPv4 echo request
2.2.
<<JUDGMENT>>
<===================
ICMPv6 Echo Request
IPv6 Header
src address : TN LINK1 IPv4 embedded IPv6 address
dst address : TN LINK0 IPv4 embedded IPv6 address
Hop Limit = 63
ICMPv6 echo request
3.1.
<===================
ICMPv4 Echo request
IPv4 Header
src address : TN LINK1 IPv4 address
dst address : TN LINK0 IPv4 address
Don't Fragment = 1
More fragments = 0
Offset = 0
TTL = 2
ICMPv4 echo request
3.2.
<<JUDGMENT>>
<===================
ICMPv6 Echo Request
IPv6 Header
src address : TN LINK1 IPv4 embedded IPv6 address
dst address : TN LINK0 IPv4 embedded IPv6 address
Hop Limit = 1
ICMPv6 echo request
4.1.
<===================
ICMPv4 Echo request
IPv4 Header
src address : TN LINK1 IPv4 address
dst address : TN LINK0 IPv4 address
Don't Fragment = 1
More fragments = 0
Offset = 0
TTL = 1
ICMPv4 echo request
4.2.
<<JUDGMENT>>
===================>
ICMPv4 Time Exceeded
IPv4 Header
src address : NUT LINK1 IPv4 address
dst address : TN LINK1 IPv4 address
ICMPv4 Time Exceeded
Code = 0
Data = ICMPv4 Echo Request, TTL = 1
<< PASS >>
NUT translates ICMPv4 with TTL = 255, 64, 2 to ICMPv6
with Hop Limit = 254, 63, 1.
NUT responds to ICMPv4 Echo Request with TTL = 1
with an ICMPv4 Time Exceeded message.
<< FAIL >>
NUT doesn't translate TTL properly, or doesn't respond
with ICMPv4 Time Exceeded messages when TTL = 1 on
incoming packages.
RFC2765
3.1. Translating IPv4 Headers into IPv6 Headers
Hop Limit:
TTL value copied from IPv4 header. Since the
translator is a router, as part of forwarding the
packet it needs to decrement either the IPv4 TTL
(before the translation) or the IPv6 Hop Limit (after
the translation). As part of decrementing the TTL or
Hop Limit the translator (as any router) needs to
check for zero and send the ICMPv4 or ICMPv6 "ttl
exceeded" error.
perldoc V6evalTool