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Update dhcp relay test for option82 stripping (#6330)
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Signed-off-by: Gang Lv ganglv@microsoft.com

What is the motivation for this PR?
dhcp relay has an option82 related pr, and we need to update e2e test to verify this issue:
sonic-net/sonic-buildimage#12033

How did you do it?
Update dhcp offer packet, add option82 and another option. After dhcp relay, option82 should be stripped.

How did you verify/test it?
I used kvm to verify this test case.
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@ganglyu @wangxin
ganglyu authored and wangxin committed Sep 28, 2022
1 parent fbcf694 commit 8b94ef0
Showing 1 changed file with 82 additions and 7 deletions.
89 changes: 82 additions & 7 deletions ansible/roles/test/files/ptftests/py3/dhcp_relay_test.py
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Original file line number Diff line number Diff line change
Expand Up @@ -90,6 +90,11 @@ class DHCPTest(DataplaneBaseTest):
DHCP_LEASE_TIME_LEN = 6
LEASE_TIME = 86400
DHCP_PKT_BOOTP_MIN_LEN = 300
DHCP_ETHER_TYPE_IP = 0x0800
DHCP_BOOTP_OP_REPLY = 2
DHCP_BOOTP_HTYPE_ETHERNET = 1
DHCP_BOOTP_HLEN_ETHERNET = 6
DHCP_BOOTP_FLAGS_BROADCAST_REPLY = 0x8000

def __init__(self):
DataplaneBaseTest.__init__(self)
Expand Down Expand Up @@ -240,8 +245,78 @@ def create_dhcp_discover_relayed_packet(self):
pkt = ether / ip / udp / bootp
return pkt

def dhcp_offer_packet(self,
eth_server="00:01:02:03:04:05",
eth_dst="06:07:08:09:10:11",
eth_client="12:13:14:15:16:17",
ip_server="0.1.2.3",
ip_dst="255.255.255.255",
ip_offered="8.9.10.11",
port_dst=DHCP_CLIENT_PORT,
netmask_client="255.255.255.0",
ip_gateway=DEFAULT_ROUTE_IP,
dhcp_lease=256,
padding_bytes=0,
set_broadcast_bit=False,
):
"""
Return a DHCPOFFER packet
Supports a few parameters:
@param eth_server MAC address of DHCP server
@param eth_dst MAC address of destination (DHCP Client, Relay agent) or broadcast (ff:ff:ff:ff:ff:ff)
@param eth_client MAC address of DHCP client
@param ip_server IP address of DHCP server
@param ip_dst IP address of destination (DHCP Client, Relay agent) or broadcast (255.255.255.255)
@param ip_offered IP address that server is assigning to client
@param ip_gateway Gateway IP Address, address of relay agent if encountered
@param port_dst Destination port of packet (default: DHCP_PORT_CLIENT)
@param netmask_client Subnet mask of client
@param dhcp_lease Time in seconds of DHCP lease
@param padding_bytes Number of '\x00' bytes to append to end of packet
Destination IP can be unicast or broadcast (255.255.255.255)
Source port is always 67 (DHCP server port)
Destination port by default is 68 (DHCP client port), but can be also be 67 (DHCP server port) if being sent to a DHCP relay agent
"""
my_chaddr = binascii.unhexlify(eth_client.replace(':', ''))
my_chaddr += b'\x00\x00\x00\x00\x00\x00'

pkt = scapy.Ether(dst=eth_dst, src=eth_server, type=self.DHCP_ETHER_TYPE_IP)
pkt /= scapy.IP(src=ip_server, dst=ip_dst, ttl=128, id=0)
pkt /= scapy.UDP(sport=self.DHCP_SERVER_PORT, dport=port_dst)
pkt /= scapy.BOOTP(
op=self.DHCP_BOOTP_OP_REPLY,
htype=self.DHCP_BOOTP_HTYPE_ETHERNET,
hlen=self.DHCP_BOOTP_HLEN_ETHERNET,
hops=0,
xid=0,
secs=0,
flags=self.DHCP_BOOTP_FLAGS_BROADCAST_REPLY if set_broadcast_bit else 0,
ciaddr=self.DEFAULT_ROUTE_IP,
yiaddr=ip_offered,
siaddr=ip_server,
giaddr=ip_gateway,
chaddr=my_chaddr,
)
# The length of option82 is 41 bytes, and dhcp relay will strip option82,
# when the length of next option is bigger than 42 bytes,
# it could introduce the overwritten issue.
pkt /= scapy.DHCP(
options=[
("message-type", "offer"),
("server_id", ip_server),
("lease_time", int(dhcp_lease)),
("subnet_mask", netmask_client),
(82, self.option82),
("vendor_class_id", "http://0.0.0.0/this_is_a_very_very_long_path/test.bin".encode('utf-8')),
("end"),
]
)
if padding_bytes:
pkt /= scapy.PADDING("\x00" * padding_bytes)
return pkt

def create_dhcp_offer_packet(self):
return testutils.dhcp_offer_packet(eth_server=self.server_iface_mac,
return self.dhcp_offer_packet(eth_server=self.server_iface_mac,
eth_dst=self.uplink_mac,
eth_client=self.client_mac,
ip_server=self.server_ip,
Expand All @@ -266,8 +341,8 @@ def create_dhcp_offer_relayed_packet(self):
# 4.) Replaces the destination IP with broadcast (255.255.255.255)
# 5.) Replaces the destination port with the DHCP client port (68)
ether = scapy.Ether(dst=self.BROADCAST_MAC, src=self.relay_iface_mac, type=0x0800)
ip = scapy.IP(src=self.relay_iface_ip, dst=self.BROADCAST_IP, len=290, ttl=64)
udp = scapy.UDP(sport=self.DHCP_SERVER_PORT, dport=self.DHCP_CLIENT_PORT, len=262)
ip = scapy.IP(src=self.relay_iface_ip, dst=self.BROADCAST_IP, ttl=64)
udp = scapy.UDP(sport=self.DHCP_SERVER_PORT, dport=self.DHCP_CLIENT_PORT)
bootp = scapy.BOOTP(op=2,
htype=1,
hlen=6,
Expand All @@ -284,13 +359,13 @@ def create_dhcp_offer_relayed_packet(self):
('server_id', self.server_ip),
('lease_time', self.LEASE_TIME),
('subnet_mask', self.client_subnet),
("vendor_class_id", "http://0.0.0.0/this_is_a_very_very_long_path/test.bin".encode('utf-8')),
('end')])

# TODO: Need to add this to the packet creation functions in PTF code first!
# If our bootp layer is too small, pad it
#pad_bytes = self.DHCP_PKT_BOOTP_MIN_LEN - len(bootp)
#if pad_bytes > 0:
# bootp /= scapy.PADDING('\x00' * pad_bytes)
pad_bytes = self.DHCP_PKT_BOOTP_MIN_LEN - len(bootp)
if pad_bytes > 0:
bootp /= scapy.PADDING('\x00' * pad_bytes)

pkt = ether / ip / udp / bootp
return pkt
Expand Down

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