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Mon, 04 Mar 2024 03:41:28 -0800 (PST) Received: from imac ([2a02:8010:60a0:0:29eb:67db:e43b:26b1]) by smtp.gmail.com with ESMTPSA id d15-20020a5d644f000000b0033e052be14fsm11941359wrw.98.2024.03.04.03.41.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 04 Mar 2024 03:41:27 -0800 (PST) From: Donald Hunter To: Jakub Kicinski Cc: davem@davemloft.net, netdev@vger.kernel.org, edumazet@google.com, pabeni@redhat.com, jiri@resnulli.us Subject: Re: [PATCH net-next 2/4] tools: ynl: allow setting recv() size In-Reply-To: <20240301230542.116823-3-kuba@kernel.org> (Jakub Kicinski's message of "Fri, 1 Mar 2024 15:05:40 -0800") Date: Mon, 04 Mar 2024 11:38:29 +0000 Message-ID: References: <20240301230542.116823-1-kuba@kernel.org> <20240301230542.116823-3-kuba@kernel.org> User-Agent: Gnus/5.13 (Gnus v5.13) Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain Jakub Kicinski writes: > 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 > --- > 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() Nit: You've added this between the declaration of async_msg_ids and where it gets populated. Otherwise LGTM. > + > 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: