From 27f0ffa39a24b169b6138f1974c123fa6df2bad2 Mon Sep 17 00:00:00 2001
From: Martin Teichmann <martin.teichmann@gmail.com>
Date: Fri, 24 Feb 2023 12:15:05 +0000
Subject: [PATCH] add PacketVar also to XDP proper
this is not actually related to the ebpfcat PacketVar, but kinda
similar.
---
ebpfcat/ebpf.rst | 16 ++++++++++++++++
ebpfcat/ebpf_test.py | 11 +++++++----
ebpfcat/xdp.py | 13 ++++++++++++-
3 files changed, 35 insertions(+), 5 deletions(-)
diff --git a/ebpfcat/ebpf.rst b/ebpfcat/ebpf.rst
index e771183..a09594e 100644
--- a/ebpfcat/ebpf.rst
+++ b/ebpfcat/ebpf.rst
@@ -141,6 +141,22 @@ is too small (by default ``XDPExitCode.PASS``). So the above example becomes::
with self.pH[12] == 8:
self.count += 1
+With the ``PacketVar`` descriptor it is possible to declare certain positions
+in the packet as variables. As parameters it takes the position within the
+packet, and the data format, following the conventions from the Python
+``struct`` package. So the above example simplifies to::
+
+ class Program(XDP):
+ minimumPacketSize = 16
+ userspace = HashMap()
+ count = userspace.globalVar()
+ etherType = PacketVar(12, "H")
+
+ def program(self):
+ with self.etherType == 8:
+ self.count += 1
+
+
Maps
----
diff --git a/ebpfcat/ebpf_test.py b/ebpfcat/ebpf_test.py
index 4dea965..b450fe2 100644
--- a/ebpfcat/ebpf_test.py
+++ b/ebpfcat/ebpf_test.py
@@ -23,7 +23,7 @@ from .ebpf import (
AssembleError, EBPF, FuncId, Opcode, OpcodeFlags, Opcode as O, LocalVar,
SubProgram, ktime)
from .hashmap import HashMap
-from .xdp import XDP
+from .xdp import XDP, PacketVar
from .bpf import ProgType, prog_test_run
@@ -903,8 +903,10 @@ class Tests(TestCase):
class P(XDP):
minimumPacketSize = 100
+ pv = PacketVar(20, "H")
+
def program(self):
- self.r3 = self.pH[22]
+ self.pv = self.pH[22]
p = P(license="GPL")
p.assemble()
@@ -913,8 +915,9 @@ class Tests(TestCase):
Instruction(opcode=O.W+O.LD, dst=0, src=1, off=4, imm=0),
Instruction(opcode=O.W+O.LD, dst=2, src=1, off=0, imm=0),
Instruction(opcode=O.LONG+O.ADD, dst=2, src=0, off=0, imm=100),
- Instruction(opcode=O.JLE+O.REG, dst=0, src=2, off=1, imm=0),
- Instruction(opcode=O.REG+O.LD, dst=3, src=9, off=22, imm=0),
+ Instruction(opcode=O.JLE+O.REG, dst=0, src=2, off=2, imm=0),
+ Instruction(opcode=O.REG+O.LD, dst=0, src=9, off=22, imm=0),
+ Instruction(opcode=O.REG+O.STX, dst=9, src=0, off=20, imm=0),
Instruction(opcode=O.LONG+O.MOV, dst=0, src=0, off=0, imm=2),
Instruction(opcode=O.EXIT, dst=0, src=0, off=0, imm=0),
])
diff --git a/ebpfcat/xdp.py b/ebpfcat/xdp.py
index db17388..0d2b518 100644
--- a/ebpfcat/xdp.py
+++ b/ebpfcat/xdp.py
@@ -24,7 +24,7 @@ from socket import AF_NETLINK, NETLINK_ROUTE, if_nametoindex
import socket
from struct import pack, unpack
-from .ebpf import EBPF
+from .ebpf import EBPF, MemoryDesc
from .bpf import ProgType
from .util import sub
@@ -152,6 +152,17 @@ class PacketSize:
return self > value - 1
+class PacketVar(MemoryDesc):
+ base_register = 9
+
+ def __init__(self, address, fmt):
+ self.address = address
+ self.fmt = fmt
+
+ def fmt_addr(self, instance):
+ return self.fmt, self.address
+
+
class XDP(EBPF):
"""the base class for XDP programs"""
minimumPacketSize = None
--
GitLab