From b187785d94c344c477808eaf9bf54101a88058a9 Mon Sep 17 00:00:00 2001
From: Martin Teichmann <martin.teichmann@gmail.com>
Date: Fri, 10 Feb 2023 11:58:56 +0000
Subject: [PATCH] move index datagram to the end of packet
not done for FastEtherCat yet, so it doesn't work
---
ebpfcat/ethercat.py | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)
diff --git a/ebpfcat/ethercat.py b/ebpfcat/ethercat.py
index 4b703e2..de406b9 100644
--- a/ebpfcat/ethercat.py
+++ b/ebpfcat/ethercat.py
@@ -193,10 +193,12 @@ class Packet:
ETHERNET_HEADER = 14
DATAGRAM_HEADER = 10
DATAGRAM_TAIL = 2
+ PACKET_HEADER = 2
+ PACKET_TAIL = 12
def __init__(self):
self.data = []
- self.size = 14
+ self.size = self.PACKET_HEADER
def append(self, cmd, data, idx, *address):
"""Append a datagram to the packet
@@ -220,13 +222,15 @@ class Packet:
An implicit empty datagram is added at the beginning of the packet
that may be used as an identifier for the packet.
"""
- ret = [pack("<HBBiHHH", self.size | 0x1000, 0, 0, index, 1 << 15, 0, 0)]
+ FOLLOW = 0x8000
+ ret = [pack("<H", (self.size + self.PACKET_TAIL) | 0x1000)]
for i, (cmd, data, *dgram) in enumerate(self.data, start=1):
ret.append(pack("<BBhHHH" if len(dgram) == 3 else "<BBiHH",
cmd.value, *dgram,
- len(data) | ((i < len(self.data)) << 15), 0))
+ len(data) | FOLLOW, 0))
ret.append(data)
ret.append(b"\0\0")
+ ret.append(pack("<BBiHHH", 0, 0, index, 0, 0, 0))
return b''.join(ret)
def __str__(self):
@@ -362,7 +366,7 @@ class EtherCat(Protocol):
p = Packet()
p.append(ECCmd.APRD, b"\0\0", 0, 0, 0x10)
ret = await self.roundtrip_packet(p)
- no, = unpack("<h", ret[16:18]) # number of terminals
+ no, = unpack("<h", ret[4:6]) # number of terminals
return no
async def find_free_address(self):
@@ -382,7 +386,9 @@ class EtherCat(Protocol):
def datagram_received(self, data, addr):
"""distribute received packets to the recipients"""
- index, = unpack("<I", data[4:8])
+ length, = unpack("<H", data[:2])
+ length &= 0x7ff
+ index, = unpack("<I", data[length-10 : length-6])
self.wait_futures[index].set_result(data)
--
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