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Message-ID: <20240301230542.116823-3-kuba@kernel.org>
Date: Fri, 1 Mar 2024 15:05:40 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: davem@...emloft.net
Cc: netdev@...r.kernel.org,
edumazet@...gle.com,
pabeni@...hat.com,
jiri@...nulli.us,
donald.hunter@...il.com,
Jakub Kicinski <kuba@...nel.org>
Subject: [PATCH net-next 2/4] tools: ynl: allow setting recv() size
Make the size of the buffer we use for recv() configurable.
The details of the buffer sizing in netlink are somewhat
arcane, we could spend a lot of time polishing this API.
Let's just leave some hopefully helpful comments for now.
This is a for-developers-only feature, anyway.
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
---
tools/net/ynl/lib/ynl.py | 21 ++++++++++++++++++---
1 file changed, 18 insertions(+), 3 deletions(-)
diff --git a/tools/net/ynl/lib/ynl.py b/tools/net/ynl/lib/ynl.py
index 92ade9105f31..bc5a526dbb99 100644
--- a/tools/net/ynl/lib/ynl.py
+++ b/tools/net/ynl/lib/ynl.py
@@ -84,6 +84,10 @@ from .nlspec import SpecFamily
return f"Netlink error: {os.strerror(-self.nl_msg.error)}\n{self.nl_msg}"
+class ConfigError(Exception):
+ pass
+
+
class NlAttr:
ScalarFormat = namedtuple('ScalarFormat', ['native', 'big', 'little'])
type_formats = {
@@ -400,7 +404,8 @@ genl_family_name_to_id = None
class YnlFamily(SpecFamily):
- def __init__(self, def_path, schema=None, process_unknown=False):
+ def __init__(self, def_path, schema=None, process_unknown=False,
+ recv_size=131072):
super().__init__(def_path, schema)
self.include_raw = False
@@ -423,6 +428,16 @@ genl_family_name_to_id = None
self.async_msg_ids = set()
self.async_msg_queue = []
+ # Note that netlink will use conservative (min) message size for
+ # the first dump recv() on the socket, our setting will only matter
+ # from the second recv() on.
+ self._recv_size = recv_size
+ # Netlink will always allocate at least PAGE_SIZE - sizeof(skb_shinfo)
+ # for a message, so smaller receive sizes will lead to truncation.
+ # Note that the min size for other families may be larger than 4k!
+ if self._recv_size < 4000:
+ raise ConfigError()
+
for msg in self.msgs.values():
if msg.is_async:
self.async_msg_ids.add(msg.rsp_value)
@@ -799,7 +814,7 @@ genl_family_name_to_id = None
def check_ntf(self):
while True:
try:
- reply = self.sock.recv(128 * 1024, socket.MSG_DONTWAIT)
+ reply = self.sock.recv(self._recv_size, socket.MSG_DONTWAIT)
except BlockingIOError:
return
@@ -854,7 +869,7 @@ genl_family_name_to_id = None
done = False
rsp = []
while not done:
- reply = self.sock.recv(128 * 1024)
+ reply = self.sock.recv(self._recv_size)
nms = NlMsgs(reply, attr_space=op.attr_set)
for nl_msg in nms:
if nl_msg.extack:
--
2.44.0
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