Fix Segment Routing Pad1 TLV definition

[yiyuandao]

In RFC 8754， 2.1.1.1, Pad1 is a single byte.

   0 1 2 3 4 5 6 7
  +-+-+-+-+-+-+-+-+
  |     Type      |
  +-+-+-+-+-+-+-+-+

but in the current implementation, Pad1 are three bytes, b'\x00\x01\x00'

raw(IPv6ExtHdrSegmentRoutingTLVPad1())

This PR fixed it.

Hope it can help.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.04%. Comparing base (316945f) to head (1d2ada8).
Report is 2 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #4611   +/-   ##
=======================================
  Coverage   81.04%   81.04%           
=======================================
  Files         365      365           
  Lines       88983    88983           
=======================================
+ Hits        72116    72120    +4     
+ Misses      16867    16863    -4     

Files with missing lines	Coverage Δ
scapy/layers/inet6.py	88.57% <100.00%> (ø)

... and 3 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[gpotter2]

That's kinda already the case:

scapy/scapy/layers/inet6.py

Lines 768 to 770 in 53d006b

	class Pad1(Packet): # IPv6 Hop-By-Hop Option
	name = "Pad1"
	fields_desc = [_OTypeField("otype", 0x00, _hbhopts)]

I wonder if there isn't a duplicate here

[yiyuandao]

That's kinda already the case:

scapy/scapy/layers/inet6.py

Lines 768 to 770 in 53d006b

	class Pad1(Packet): # IPv6 Hop-By-Hop Option
	name = "Pad1"
	fields_desc = [_OTypeField("otype", 0x00, _hbhopts)]

I wonder if there isn't a duplicate here

Indeed, they are identical functions.

but class Pad1 is for Destination Options and Hop-by-Hop Options.
and class IPv6ExtHdrSegmentRoutingTLVPad1 is for Segment Routing Header TLVs.

In my opinion, it appears they are distinct. I think that Pv6ExtHdrSegmentRoutingTLVPad1 ought to have a unique definition of its own.

[gpotter2]

Thanks for the PR & sorry for the huge delay !