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@kernel.org>
Reviewed-by: Donald Hunter <donald.hunter@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/tools/net/ynl/lib/ynl.py b/tools/net/ynl/lib/ynl.py
index 92ade91..c3ff5be 100644
--- a/tools/net/ynl/lib/ynl.py
+++ b/tools/net/ynl/lib/ynl.py
@@ -84,6 +84,10 @@
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 @@
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=0):
super().__init__(def_path, schema)
self.include_raw = False
@@ -415,6 +420,16 @@
except KeyError:
raise Exception(f"Family '{self.yaml['name']}' not supported by the kernel")
+ # 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 if recv_size else 131072
+ # 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()
+
self.sock = socket.socket(socket.AF_NETLINK, socket.SOCK_RAW, self.nlproto.proto_num)
self.sock.setsockopt(Netlink.SOL_NETLINK, Netlink.NETLINK_CAP_ACK, 1)
self.sock.setsockopt(Netlink.SOL_NETLINK, Netlink.NETLINK_EXT_ACK, 1)
@@ -799,7 +814,7 @@
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 @@
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:
