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Sat, 14 Mar 2026 10:44:29 -0700 (PDT) From: Tom Herbert To: davem@davemloft.net, kuba@kernel.org, netdev@vger.kernel.org, justin.iurman@uliege.be, willemdebruijn.kernel@gmail.com, pabeni@redhat.com Cc: Tom Herbert Subject: [net-next v8 09/10] test: Add ext_hdr.py in networking selftests Date: Sat, 14 Mar 2026 10:43:32 -0700 Message-ID: <20260314174333.46406-10-tom@herbertland.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260314174333.46406-1-tom@herbertland.com> References: <20260314174333.46406-1-tom@herbertland.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Add ext_hdr.py that contains various Extension Header format definitions and related helper functions. This includes the Make_EH_Chain function that creates an Extension Header chain based on an input list. The input list has the format: [(, ), (, ), ... (, )] where is "H" for Hop-by-Hop Options, "D" for Destination Options, "R" for Routing Header, "F" for Fragment header, "A" for Authentication Header, and "E" for ESP header. is specific to the type of extension header. For Hop-by-Hop and Destination Options is a list of options in the format: [(, ), (, ), ... (, )] For the Routing Header, is a list of SIDs in the format: [IPv6_address, IPv6_address, ... IPv6_address] For the Fragment Header, is the identifier number Authentication and ESP are not currently supported by Make_EH_Chain Signed-off-by: Tom Herbert --- tools/testing/selftests/net/ext_hdr.py | 385 +++++++++++++++++++++++++ 1 file changed, 385 insertions(+) create mode 100755 tools/testing/selftests/net/ext_hdr.py diff --git a/tools/testing/selftests/net/ext_hdr.py b/tools/testing/selftests/net/ext_hdr.py new file mode 100755 index 000000000000..bfb7da4a7c88 --- /dev/null +++ b/tools/testing/selftests/net/ext_hdr.py @@ -0,0 +1,385 @@ +#!/usr/bin/env python3 +# SPDX-License-Identifier: GPL-2.0 + +# Helper functions for creating extension headers using scapy + +import ctypes +import shlex +import socket +import sys +import subprocess +import scapy +import proto_nums + + +# Read a sysctl +def sysctl_read(name): + try: + # shlex.split helps handle arguments correctly + command = shlex.split(f"sysctl -n {name}") + # Use check=True to raise an exception if the command fails + result = subprocess.run(command, check=True, + capture_output=True, text=True) + value = result.stdout.strip() + except subprocess.CalledProcessError as ex: + print(f"Error reading sysctl: {ex.stderr}") + except FileNotFoundError: + print("The 'sysctl' command was not found. " + "Check your system's PATH.") + + return int(value) + +# Common definitions for Destination and Hop-by-Hop options + +# Common Destination and Hop-by-Hop Options header +class HbhDstOptions(ctypes.BigEndianStructure): + _pack_ = 1 + _fields_ = [ + ("next_hdr", ctypes.c_uint8), + ("hdr_ext_len", ctypes.c_uint8) + ] + + def __init__(self, next_hdr, length): + self.next_hdr = next_hdr + self.hdr_ext_len = length + +# Common single Destination and Hop-by-Hop Option header +class HbhDstOption(ctypes.BigEndianStructure): + _pack_ = 1 + _fields_ = [ + ("opt_type", ctypes.c_uint8), + ("opt_data_len", ctypes.c_uint8), + ] + + def __init__(self, opt_type, length): + self.opt_type = opt_type + self.opt_data_len = length + +# Make PAD1 option +def make_hbh_dst_option_pad1(): + opt_bytes = bytearray(1) + opt_bytes[0] = proto_nums.HBHDst_Types.HBHDST_TYPE_PAD1.value + return (scapy.all.Raw(opt_bytes), 1) + +# Make a full DestOpt or HBH Option with some length +def make_hbh_dst_option_with_data(opt_type, opt_len): + hdr = scapy.all.Raw(load=HbhDstOption(opt_type, opt_len)) + opt_bytes = scapy.all.Raw(bytearray(opt_len)) + allhdr = hdr/opt_bytes + return (scapy.all.Raw(allhdr), 2 + opt_len) + +# Make PADN option +def make_hbh_dst_option_pad_n(opt_len): + return make_hbh_dst_option_with_data( + proto_nums.HBHDst_Types.HBHDST_TYPE_PADN.value, opt_len) + +# Make a Destination or Hop-by-Hop Options list. Input is list of pairs as +# (type, length). Option data is set to zeroes. +# +# Return value is (hdr, len, outcome) where hdr is the raw bytes and length +# is the length of the header including two bytes for the common extension +# header (the returned header does not include the two byte common header). +# outcome is True or False depending on whether the options are expected to +# exceed a sysctl limit and would be dropped +def make_hbh_dst_options_list(opt_list, max_cnt, max_len): + hdr = scapy.all.Raw() + eh_len = 0 + + num_non_padding_opts = 0 + max_consect_pad_len = 0 + + consect_padlen = 0 + + # Create the set of options + for opt_type, jlen in opt_list: + if opt_type == proto_nums.HBHDst_Types.HBHDST_TYPE_PAD1.value: + # PAD1 is a special case + pair = make_hbh_dst_option_pad1() + consect_padlen += pair[1] + else: + pair = make_hbh_dst_option_with_data(opt_type, jlen) + + if opt_type == proto_nums.HBHDst_Types.HBHDST_TYPE_PADN.value: + consect_padlen += pair[1] + else: + if consect_padlen > max_consect_pad_len: + max_consect_pad_len = consect_padlen + consect_padlen = 0 + num_non_padding_opts += 1 + + # Append the option, add to cumulative length + hdr = hdr/pair[0] + eh_len += pair[1] + + # Add two to length to account for two byte extension header + eh_len += 2 + + if eh_len % 8 != 0: + # The extension header length must be a multiple of eight bytes. + # If we're short add a padding option + plen = 8 - (eh_len % 8) + if plen == 1: + pair = make_hbh_dst_option_pad1() + else: + pair = make_hbh_dst_option_pad_n(plen - 2) + + consect_padlen += pair[1] + hdr = hdr/pair[0] + eh_len += plen + + if consect_padlen > max_consect_pad_len: + max_consect_pad_len = consect_padlen + + outcome = True + if num_non_padding_opts > max_cnt: + # The number of options we created is greater then the sysctl + # limit, so we expect the packet to be dropped + outcome = False + if eh_len > max_len: + # The length of the extension is greater then the sysctl limit, + # so we expect the packet to be dropped + outcome = False + if max_consect_pad_len > 7: + # The maximum consecutive number of bytes of padding is + # greater than seven, so we expect the packet to be dropped + outcome = False + + return (hdr, eh_len - 2, outcome) + +# Make a full Hop-by-Hop or Destination Options header +def make_full_hbh_dst_options_list(next_hdr, opt_list, max_cnt, max_len): + pair = make_hbh_dst_options_list(opt_list, max_cnt, max_len) + opt_len = pair[1] + 2 + + opts = HbhDstOptions(next_hdr, (opt_len - 1) // 8) + hdr = scapy.all.Raw(load=opts)/pair[0] + + return (hdr, opt_len, pair[2]) + +# Routing header definitions + +# Base Routing Header +class RoutingHdr(ctypes.BigEndianStructure): + _pack_ = 1 + _fields_ = [ + ("next_hdr", ctypes.c_uint8), + ("hdr_ext_len", ctypes.c_uint8), + ("routing_type", ctypes.c_uint8), + ("segments_left", ctypes.c_uint8) + ] + +# SRv6 Routing Header +class Srv6RoutingHdr(ctypes.BigEndianStructure): + _pack_ = 1 + _fields_ = [ + ("rh", RoutingHdr), + ("last_entry", ctypes.c_uint8), + ("flags", ctypes.c_uint8), + ("tags", ctypes.c_uint16), + # Variable list + # TLV options + ] + + def __init__(self, next_hdr, hdr_ext_len, segments_left, last_entry): + self.rh.next_hdr = next_hdr + self.rh.hdr_ext_len = hdr_ext_len + self.rh.routing_type = proto_nums.RoutingTypes.ROUTING_TYPE_SRH.value + self.rh.segments_left = segments_left + + self.last_entry = last_entry + +# Make an SRv6 Routing Header (with no segments left) +def make_srv6_routing_hdr(next_hdr, sids): + + bhdr = scapy.all.Raw() + num_sids = 0 + + # Set up each SID in the list + for sid in sids: + sid_bytes = socket.inet_pton(socket.AF_INET6, sid) + bhdr = bhdr/scapy.all.Raw(load=sid_bytes) + num_sids += 1 + + eh_len = num_sids * 16 + + hdr = Srv6RoutingHdr(next_hdr, eh_len // 8, 0, num_sids - 1) + + bhdr = scapy.all.Raw(load=hdr)/bhdr + + return (bhdr, eh_len + 8, True) + +# Fragment header + +# Basic Fragment Header +class FragmentHdr(ctypes.BigEndianStructure): + _pack_ = 1 + _fields_ = [ + ("next_hdr", ctypes.c_uint8), + ("rsvd", ctypes.c_uint8), + ("fragment_offset", ctypes.c_uint16, 13), + ("rsvd2", ctypes.c_uint16, 2), + ("more", ctypes.c_uint16, 1), + ("identfication", ctypes.c_uint32), + ] + + def __init__(self, next_hdr, fragment_offset, more, ident): + self.next_hdr = next_hdr + self.fragment_offset = fragment_offset + self.more = more + self.identfication = ident + +# Make a raw fragment header +def make_fragment_hdr(next_hdr, fragment_offset, more, ident): + hdr = FragmentHdr(next_hdr, fragment_offset, more, ident) + + return (scapy.all.Raw(load=hdr), 8, True) + +# Authentication Header + +# Base Authentication Header +class AuthHdr(ctypes.BigEndianStructure): + _pack_ = 1 + _fields_ = [ + ("next_hdr", ctypes.c_uint8), + ("payload_len", ctypes.c_uint8), + ("spi", ctypes.c_uint32) + # ICV is variable length + ] + + def __init__(self, next_hdr, payload_len, spi): + self.next_hdr = next_hdr + self.payload_len = payload_len + self.spi = spi + +# ESP + +# Base ESP header +class EspHdr(ctypes.BigEndianStructure): + _pack_ = 1 + _fields_ = [ + ("spi", ctypes.c_uint32), + ("seqno", ctypes.c_uint32) + # Payload data + padding + # ICV is variable length + ] + + def __init__(self, spi, seqno): + self.spi = spi + self.seqno = seqno + +# Check if EH list is out of order +def check_eh_order(eh_list): + # OOO is okay if sysctl is not enforcing in order + do_check = sysctl_read("net.ipv6.enforce_ext_hdr_order") + + seen = 0 + for eh_type, _args in eh_list: + if eh_type == "H": + order = proto_nums.EH_Order.IPV6_EXT_HDR_ORDER_HOP.value + elif eh_type == "D": + if (seen & + proto_nums.EH_Order.IPV6_EXT_HDR_ORDER_ROUTING.value): + order = proto_nums.EH_Order.IPV6_EXT_HDR_ORDER_DEST.value + else: + order = proto_nums.EH_Order.IPV6_EXT_HDR_ORDER_DEST_BEFORE_RH.value + elif eh_type == "R": + order = proto_nums.EH_Order.IPV6_EXT_HDR_ORDER_ROUTING.value + elif eh_type == "F": + order = proto_nums.EH_Order.IPV6_EXT_HDR_ORDER_FRAGMENT.value + if seen & order != 0: + # Linux stack doesn't allow more than one + # Fragment Header in a packet + return False + elif eh_type == "A": + order = proto_nums.EH_Order.IPV6_EXT_HDR_ORDER_AUTH.value + elif eh_type == "E": + order = proto_nums.EH_Order.IPV6_EXT_HDR_ORDER_ESP.value + + if (do_check and seen >= order): + return False + seen |= order + + return True + +# Compute the next headers for an EH chain. Returns a new list of EHs +# with the next header attached to each element +def compute_next_hdrs(next_hdr, eh_list): + nlist = [] + + # Run through the list in reverse and set the next header up for each + # enty + for eh_type, args in reversed(eh_list): + entry = (eh_type, args, next_hdr) + nlist.insert(0, entry) + if eh_type == "H": + next_hdr = proto_nums.IP_Proto.IP_PROTO_HOPOPT.value + elif eh_type == "D": + next_hdr = proto_nums.IP_Proto.IP_PROTO_IPv6_Opts.value + elif eh_type == "R": + next_hdr = proto_nums.IP_Proto.IP_PROTO_IPv6_Route.value + elif eh_type == "F": + next_hdr = proto_nums.IP_Proto.IP_PROTO_IPv6_Frag.value + elif eh_type == "A": + next_hdr = proto_nums.IP_Proto.IP_PROTO_AH.value + elif eh_type == "E": + next_hdr = proto_nums.IP_Proto.IP_PROTO_ESP.value + + return nlist, next_hdr + +# Make an extension header chain from a list +# The list contains a set of pairs in the form (, ) +# is: +# "H"-- Hop-by-Hop Options +# "D"-- Destination Options +# "R"-- Routing Header +# "F"-- Fragment Header +# "A"-- Authentication Header +# "E"-- ESP +# +# is specific to EH type +def make_eh_chain(next_hdr, eh_list): + nlist = [] + + # Run through the list in reverse and set the next header up for each + # enty + nlist, next_hdr = compute_next_hdrs(next_hdr, eh_list) + + outcome = check_eh_order(eh_list) + + hdr = scapy.all.Raw() + eh_len = 0 + + for eh_type, args, nnext_hdr in reversed(nlist): + if eh_type == "H": + # args is a list of (, ) pairs + pair = make_full_hbh_dst_options_list(nnext_hdr, args, + sysctl_read("net.ipv6.max_hbh_opts_number"), + sysctl_read("net.ipv6.max_hbh_length")) + elif eh_type == "D": + # args is a list of (, ) pairs + pair = make_full_hbh_dst_options_list(nnext_hdr, args, + sysctl_read("net.ipv6.max_dst_opts_number"), + sysctl_read("net.ipv6.max_dst_opts_length")) + elif eh_type == "R": + # args is a list of IPv6 address string + pair = make_srv6_routing_hdr(nnext_hdr, args) + elif eh_type == "F": + # Arg is () + pair = make_fragment_hdr(nnext_hdr, 0, False, args) + elif eh_type == "A": + print("Auth type not supported for test") + sys.exit(1) + elif eh_type == "E": + print("ESP type not supported for test") + sys.exit(1) + else: + print("Unknown EH type character") + sys.exit(1) + + hdr = pair[0]/hdr + eh_len += pair[1] + + if pair[2] is False: + outcome = False + + return (hdr, eh_len, next_hdr, outcome) -- 2.43.0