From 7c93a88785dae6b61dc736b46594d088989e484b Mon Sep 17 00:00:00 2001 From: Jakub Kicinski Date: Mon, 4 Mar 2024 21:33:08 -0800 Subject: [PATCH] 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 Reviewed-by: Donald Hunter Signed-off-by: David S. Miller --- 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..c3ff5be33e4e 100644 --- a/tools/net/ynl/lib/ynl.py +++ b/tools/net/ynl/lib/ynl.py @@ -84,6 +84,10 @@ class NlError(Exception): 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 SpaceAttrs: 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 @@ class YnlFamily(SpecFamily): 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 @@ class YnlFamily(SpecFamily): 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 @@ class YnlFamily(SpecFamily): 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: