def _encode(self, outstream):
fld_size = IntField(32, False)
fld_data = RawBytes(0)
if len(self.section.interfaces) > 1:
# Spec is a bit ambiguous here. Section 4.4 says "it MUST
# be assumed that all the Simple Packet Blocks have been captured
# on the interface previously specified in the first Interface
# Description Block." but later adds "A Simple Packet Block cannot
# be present in a Section that has more than one interface because
# of the impossibility to refer to the correct one (it does not
# contain any Interface ID field)." Why would it say "the first"
# IDB and not "the only" IDB if this was really forbidden?
strictness.problem(
"writing SimplePacket for section with multiple interfaces")
if strictness.should_fix():
# Can't fix this. The IDBs have already been written.
pass
snap_len = self.interface.snaplen
if snap_len > 0 and snap_len < self.captured_len:
# This isn't a strictness issue, it *will* break other readers
# if we write more bytes than the snaplen says to expect.
fld_size.encode(self.packet_len,
outstream,
endianness=self.section.endianness)
fld_data.encode(self.packet_data[:snap_len], outstream)
else:
fld_size.encode(self.packet_len,
outstream,
endianness=self.section.endianness)
fld_data.encode(self.packet_data, outstream)
def write_options(stream, options):
"""
Each option is composed by:
- option_code (uint16)
- value_length (uint16)
- value (value_length-sized binary data)
The end marker is simply an option with code ``0x0000``, length 0,
and no payload
"""
if not options:
# Options are optional; if there are none we don't need opt_endofopt
return
for key in options:
code = options._field_names[key]
values = options.get_all_raw(key)
if len(values) > 1 and not options.schema[code].multiple:
strictness.problem(
"writing repeated option {} '{}' not permitted by pcapng spec".
format(code, options._get_name_alias(code)))
if strictness.should_fix():
values = values[:1]
for value in values:
write_int(code, stream, 16, False, options.endianness)
write_int(len(value), stream, 16, False, options.endianness)
write_bytes_padded(stream, value)
# Write the end marker
write_int(0, stream, 32, False, options.endianness)
def _check_multiples(self, code):
"""Check if a non-repeatable option is repeated"""
if len(self.data[code]) > 1 and not self.schema[code].multiple:
strictness.problem(
"repeated option {} '{}' not permitted by pcapng spec".format(
code, self._get_name_alias(code)))
if strictness.should_fix():
self.data[code] = self.data[code][:1]
def write(self, outstream):
if len(self.section.interfaces) < 1:
strictness.problem(
"writing {cls} for section with no interfaces".format(
cls=self.__class__.__name__))
if strictness.should_fix():
# Only way to "fix" is to not write the block
return
super(BlockWithInterfaceMixin, self).write(outstream)
def write(self, outstream):
strictness.problem("Packet Block is obsolete and must not be used")
if strictness.should_fix():
self.enhanced().write(outstream)
else:
super(ObsoletePacket, self).write(outstream)