From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from ganesha.gnumonks.org (ganesha.gnumonks.org [213.95.27.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6E9861946AA for ; Mon, 30 Sep 2024 17:10:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.95.27.120 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727716232; cv=none; b=SOGI2OOyZB2hlB29t9FWko1W/1N+gJ+7JedLxF060pUhNEDlCq9GM1mmwcs97uBYDijnZi79UQFFbK4tl7ce2FhHGT1/kXklc3gFasVpowQtYu8lZtArhXNtgZUWF7xEi7hjkVgbwKhJGz/pjquaHL4Bd+QyFF4hCq6C2G1s8jU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727716232; c=relaxed/simple; bh=lT7z4woZpV3MYMAtOnN2stmT6hz9j8fiqL9UG7JC7Gk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=nCd5M/y+e1IlTs67SFkvtf8RnYDetYYAsol8eEHkeTCmFkq3mRJo0uTSzJwoicJygc9OHujrD8M6Guk+DzS6vQp5Np3P8vsyrINN6bI5EN2jUVm8zpajXoFjL4rOwI4fD1b9DIODJ96Q/nTBX6Gl4kEMtz0dOgZUAruT5cJUjvA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=netfilter.org; spf=pass smtp.mailfrom=gnumonks.org; arc=none smtp.client-ip=213.95.27.120 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=netfilter.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gnumonks.org Received: from [78.30.37.63] (port=58430 helo=gnumonks.org) by ganesha.gnumonks.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1svJui-008T0u-RO; Mon, 30 Sep 2024 19:10:27 +0200 Date: Mon, 30 Sep 2024 19:10:24 +0200 From: Pablo Neira Ayuso To: Petr Machata Cc: Jakub Kicinski , Danielle Ratson , Phil Sutter , "netfilter-devel@vger.kernel.org" , "fw@strlen.de" , mlxsw Subject: Re: [PATCH libmnl] src: attr: Add mnl_attr_get_uint() function Message-ID: References: <20240731063551.1577681-1-danieller@nvidia.com> <20240930134509.489b54df@kernel.org> <87cyklm7i2.fsf@nvidia.com> Precedence: bulk X-Mailing-List: netfilter-devel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: X-Spam-Score: -1.9 (-) On Mon, Sep 30, 2024 at 07:01:42PM +0200, Pablo Neira Ayuso wrote: > On Mon, Sep 30, 2024 at 06:25:17PM +0200, Petr Machata wrote: > > > > Pablo Neira Ayuso writes: > > > > > On Mon, Sep 30, 2024 at 01:45:09PM +0200, Jakub Kicinski wrote: > > >> On Mon, 30 Sep 2024 12:56:20 +0200 Pablo Neira Ayuso wrote: > > >> > On Mon, Sep 30, 2024 at 12:28:08PM +0200, Pablo Neira Ayuso wrote: > > >> > > On Sun, Sep 29, 2024 at 10:42:44AM +0000, Danielle Ratson wrote: > > >> > > > Hi, > > >> > > > > > >> > > > Is there a plan to build a new version soon? > > >> > > > I am asking since I am planning to use this function in ethtool. > > >> > > > > >> > > ASAP > > >> > > > >> > but one question before... Is this related to NLA_UINT in the kernel? > > >> > > > >> > /** > > >> > * nla_put_uint - Add a variable-size unsigned int to a socket buffer > > >> > * @skb: socket buffer to add attribute to > > >> > * @attrtype: attribute type > > >> > * @value: numeric value > > >> > */ > > >> > static inline int nla_put_uint(struct sk_buff *skb, int attrtype, u64 value) > > >> > { > > >> > u64 tmp64 = value; > > >> > u32 tmp32 = value; > > >> > > > >> > if (tmp64 == tmp32) > > >> > return nla_put_u32(skb, attrtype, tmp32); > > >> > return nla_put(skb, attrtype, sizeof(u64), &tmp64); > > >> > } > > >> > > > >> > if I'm correct, it seems kernel always uses either u32 or u64. > > >> > > > >> > Userspace assumes u8 and u16 are possible though: > > >> > > > >> > +/** > > >> > + * mnl_attr_get_uint - returns 64-bit unsigned integer attribute. > > >> > + * \param attr pointer to netlink attribute > > >> > + * > > >> > + * This function returns the 64-bit value of the attribute payload. > > >> > + */ > > >> > +EXPORT_SYMBOL uint64_t mnl_attr_get_uint(const struct nlattr *attr) > > >> > +{ > > >> > + switch (mnl_attr_get_payload_len(attr)) { > > >> > + case sizeof(uint8_t): > > >> > + return mnl_attr_get_u8(attr); > > >> > + case sizeof(uint16_t): > > >> > + return mnl_attr_get_u16(attr); > > >> > + case sizeof(uint32_t): > > >> > + return mnl_attr_get_u32(attr); > > >> > + case sizeof(uint64_t): > > >> > + return mnl_attr_get_u64(attr); > > >> > + } > > >> > + > > >> > + return -1ULL; > > >> > +} > > >> > > > >> > Or this is an attempt to provide a helper that allows you fetch for > > >> > payload value of 2^3..2^6 bytes? > > >> > > >> No preference here, FWIW. Looks like this patch does a different thing > > >> than the kernel. But maybe a broader "automatic" helper is useful for > > >> user space code. > > > > > > Not sure. @Danielle: could you clarify your intention? > > > > This follows the iproute2 helper, where I was asked to support >32-bit > > fields purely as a service to the users, so that one helper can be used > > for any integral field. > > Which helper are your referring to? Is it modeled after NLA_UINT? > > I don't think this patch is fine. This also returns -1ULL so there is > no way to know if size is not correct or payload length is 64 bits > using UINT64_MAX? I found it: static inline __u64 rta_getattr_uint(const struct rtattr *rta) This only has one user in the tree so far, right? include/libnetlink.h:static inline __u64 rta_getattr_uint(const struct rtattr *rta) ip/ipnexthop.c: nh_grp_stats->packets = rta_getattr_uint(rta); ip/ipnexthop.c: nh_grp_stats->packets_hw = rta_getattr_uint(rta); is this attribute for ipnexthop of NLA_UINT type?