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DHCP_am: support multiple nameservers #4834

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Merged
merged 2 commits into from
Sep 15, 2025
Merged

DHCP_am: support multiple nameservers #4834

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fa7d1d5
DHCP_am: support multiple nameservers
mzen17 Jan 11, 2025
7711b1f
Fix dhcpd IPython test
gpotter2 Sep 15, 2025
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39 changes: 29 additions & 10 deletions scapy/layers/dhcp.py
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Original file line number Diff line number Diff line change
Expand Up @@ -61,6 +61,13 @@
from scapy.error import warning
from scapy.config import conf

# Typing imports
from typing import (
List,
Optional,
Union,
)

dhcpmagic = b"c\x82Sc"


Expand Down Expand Up @@ -601,27 +608,33 @@ class BOOTP_am(AnsweringMachine):
filter = "udp and port 68 and port 67"

def parse_options(self,
pool=Net("192.168.1.128/25"),
network="192.168.1.0/24",
gw="192.168.1.1",
nameserver=None,
domain=None,
renewal_time=60,
lease_time=1800,
pool: Union[Net, List[str]] = Net("192.168.1.128/25"),
network: str = "192.168.1.0/24",
gw: str = "192.168.1.1",
nameserver: Union[str, List[str]] = None,
domain: Optional[str] = None,
renewal_time: int = 60,
lease_time: int = 1800,
**kwargs):
"""
:param pool: the range of addresses to distribute. Can be a Net,
a list of IPs or a string (always gives the same IP).
:param network: the subnet range
:param gw: the gateway IP (can be None)
:param nameserver: the DNS server IP (by default, same than gw)
:param nameserver: the DNS server IP (by default, same than gw).
This can also be a list.
:param domain: the domain to advertise (can be None)

Other DHCP parameters can be passed as kwargs. See DHCPOptions in dhcp.py.
For instance::

dhcpd(pool=Net("10.0.10.0/24"), network="10.0.0.0/8", gw="10.0.10.1",
classless_static_routes=["1.2.3.4/32:9.8.7.6"])

Other example with different options::

dhcpd(pool=Net("10.0.10.0/24"), network="10.0.0.0/8", gw="10.0.10.1",
nameserver=["8.8.8.8", "4.4.4.4"], domain="DOMAIN.LOCAL")
"""
self.domain = domain
netw, msk = (network.split("/") + ["32"])[:2]
Expand All @@ -630,7 +643,13 @@ def parse_options(self,
self.network = ltoa(atol(netw) & msk)
self.broadcast = ltoa(atol(self.network) | (0xffffffff & ~msk))
self.gw = gw
self.nameserver = nameserver or gw
if nameserver is None:
self.nameserver = (gw,)
elif isinstance(nameserver, str):
self.nameserver = (nameserver,)
else:
self.nameserver = tuple(nameserver)

if isinstance(pool, str):
pool = Net(pool)
if isinstance(pool, Iterable):
Expand Down Expand Up @@ -691,7 +710,7 @@ def make_reply(self, req):
("server_id", self.gw),
("domain", self.domain),
("router", self.gw),
("name_server", self.nameserver),
("name_server", *self.nameserver),
("broadcast_address", self.broadcast),
("subnet_mask", self.netmask),
("renewal_time", self.renewal_time),
Expand Down
11 changes: 11 additions & 0 deletions test/answering_machines.uts
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Original file line number Diff line number Diff line change
Expand Up @@ -39,12 +39,23 @@ test_am(BOOTP_am,
def check_DHCP_am_reply(packet):
assert DHCP in packet and len(packet[DHCP].options)
assert ("domain", b"localnet") in packet[DHCP].options
assert ('name_server', '192.168.1.1') in packet[DHCP].options

def check_ns_DHCP_am_reply(packet):
assert DHCP in packet and len(packet[DHCP].options)
assert ("domain", b"localnet") in packet[DHCP].options
assert ('name_server', '1.1.1.1', '2.2.2.2') in packet[DHCP].options

test_am(DHCP_am,
Ether()/IP()/UDP()/BOOTP(op=1)/DHCP(options=[('message-type', 'request')]),
check_DHCP_am_reply,
domain="localnet")

test_am(DHCP_am,
Ether()/IP()/UDP()/BOOTP(op=1)/DHCP(options=[('message-type', 'request')]),
check_ns_DHCP_am_reply,
domain="localnet",
nameserver=["1.1.1.1", "2.2.2.2"])

= ARP_am
def check_ARP_am_reply(packet):
Expand Down
11 changes: 10 additions & 1 deletion test/scapy/layers/dhcp.uts
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Original file line number Diff line number Diff line change
Expand Up @@ -125,5 +125,14 @@ assert DHCPRevOptions['static-routes'][0] == 33

assert dhcpd
import IPython
assert IPython.lib.pretty.pretty(dhcpd) == '<function scapy.ansmachine.dhcpd(self, pool=Net("192.168.1.128/25"), network=\'192.168.1.0/24\', gw=\'192.168.1.1\', nameserver=None, domain=None, renewal_time=60, lease_time=1800, **kwargs)>'

result = IPython.lib.pretty.pretty(dhcpd)
result

# 3 results depending on the Python version
assert result in [
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Looks like it fails on Fedora Rawhide (with Python 3.14.0rc2):

###(006)=[failed] Check that the dhcpd alias is properly defined and documented

>>> assert dhcpd
>>> import IPython
>>> 
>>> result = IPython.lib.pretty.pretty(dhcpd)
>>> result
'<function scapy.ansmachine.dhcpd(self, pool: scapy.base_classes.Net | List[str] = Net("192.168.1.128/25"), network: str = \'192.168.1.0/24\', gw: str = \'192.168.1.1\', nameserver: str | List[str] = None, domain: str | None = None, renewal_time: int = 60, lease_time: int = 1800, **kwargs)>'
>>> 
>>> assert result in [
...     '<function scapy.ansmachine.dhcpd(self, pool: Union[scapy.base_classes.Net, List[str]] = Net("192.168.1.128/25"), network: str = \'192.168.1.0/24\', gw: str = \'192.168.1.1\', nameserver: Union[str, List[str]] = None, domain: Optional[str] = None, renewal_time: int = 60, lease_time: int = 1800, **kwargs)>',
...     '<function scapy.ansmachine.dhcpd(self, pool: Union[scapy.base_classes.Net, List[str]] = Net("192.168.1.128/25"), network: str = \'192.168.1.0/24\', gw: str = \'192.168.1.1\', nameserver: Union[str, List[str]] = None, domain: Union[str, NoneType] = None, renewal_time: int = 60, lease_time: int = 1800, **kwargs)>',
...     '<function scapy.ansmachine.dhcpd(self, pool=Net("192.168.1.128/25"), network=\'192.168.1.0/24\', gw=\'192.168.1.1\', nameserver=None, domain=None, renewal_time=60, lease_time=1800, **kwargs)>',
... ]
AssertionError

https://download.copr.fedorainfracloud.org/results/packit/evverx-scapy-2/fedora-rawhide-aarch64/09564744-scapy/builder-live.log.gz

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Thanks ! See befe516

This varies a LOT depending on the Python version hehe ^^

'<function scapy.ansmachine.dhcpd(self, pool: Union[scapy.base_classes.Net, List[str]] = Net("192.168.1.128/25"), network: str = \'192.168.1.0/24\', gw: str = \'192.168.1.1\', nameserver: Union[str, List[str]] = None, domain: Optional[str] = None, renewal_time: int = 60, lease_time: int = 1800, **kwargs)>',
'<function scapy.ansmachine.dhcpd(self, pool: Union[scapy.base_classes.Net, List[str]] = Net("192.168.1.128/25"), network: str = \'192.168.1.0/24\', gw: str = \'192.168.1.1\', nameserver: Union[str, List[str]] = None, domain: Union[str, NoneType] = None, renewal_time: int = 60, lease_time: int = 1800, **kwargs)>',
'<function scapy.ansmachine.dhcpd(self, pool=Net("192.168.1.128/25"), network=\'192.168.1.0/24\', gw=\'192.168.1.1\', nameserver=None, domain=None, renewal_time=60, lease_time=1800, **kwargs)>',
]

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