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Fix UDP checksum of odd-length packets

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Odd length packets were incorrectly handled, fix
the packet construction.
This commit is contained in:
Jarrod Johnson 2020-03-26 16:59:58 -04:00
parent 16209bc3d6
commit 92e657b987
1 changed files with 12 additions and 7 deletions
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19
confluent_server/confluent/discovery/protocols/pxe.py
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@ -40,9 +40,7 @@ udphdr = b'\x00\x43\x00\x44\x00\x00\x00\x00'
def _ipsum(data):
currsum = 0
if len(data) % 2:
append = bytearray(2)
append[0] = data[-1]
currsum = struct.unpack('!H', append)
currsum = struct.unpack('!B', data[-1:])[0] << 8
data = memoryview(data)
data = data[:-1]
for datum in struct.unpack('!' + 'H' * (len(data) // 2), data):
@ -50,6 +48,8 @@ def _ipsum(data):
if currsum >> 16:
currsum &= 0xffff
currsum += 1
if currsum == 0:
currsum = 0xffff
return currsum
class sockaddr_ll(ctypes.Structure):
@ -342,7 +342,7 @@ def remap_nodes(nodeattribs, configmanager):
staticassigns = {}
def check_reply(node, info, packet, sock, cfg, reqview):
replen = 286 # default is going to be 286
replen = 275 # default is going to be 286
cfd = cfg.get_node_attributes(node, ('deployment.*'))
profile = cfd.get(node, {}).get('deployment.pendingprofile', {}).get('value', None)
myipn = info['netinfo']['recvip']
@ -398,7 +398,12 @@ def check_reply(node, info, packet, sock, cfg, reqview):
# boot filename and such in the DHCP packet
# we will simply always do it to provide the boot payload in a consistent
# matter to both dhcp-elsewhere and fixed ip clients
repview[274:285] = b'\x3c\x09PXEClient'
if info['architecture'] == 'uefi-httpboot':
repview[replen - 1:replen + 11] = b'\x3c\x0aHTTPClient'
replen += 12
else:
repview[replen - 1:replen + 10] = b'\x3c\x09PXEClient'
replen += 11
if netmask:
repview[replen - 1:replen + 1] = b'\x01\x04'
repview[replen + 1:replen + 5] = netmask
@ -419,8 +424,8 @@ def check_reply(node, info, packet, sock, cfg, reqview):
curripsum = ~(_ipsum(constiphdrsum + pktlen + myipn)) & 0xffff
repview[10:12] = struct.pack('!H', curripsum)
repview[24:26] = struct.pack('!H', replen + 8)
datasum = _ipsum(repview[12:replen + 28].tobytes() + b'\x00\x11' +
repview[24:26].tobytes())
datasum = _ipsum(b'\x00\x11' + repview[24:26].tobytes() +
repview[12:replen + 28].tobytes())
datasum = ~datasum & 0xffff
repview[26:28] = struct.pack('!H', datasum)
tsock = socket.socket(socket.AF_PACKET, socket.SOCK_DGRAM,