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 CAA44194AD1 for ; Mon, 30 Sep 2024 17:01:45 +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=1727715709; cv=none; b=shlKm95otidYRNSC7d7O0dIpK1zbvlTmBW7k4IaoVhbk74D5eEPzvoPeK3920aOym8IUOxNBaowiKvVP3IcgoquMXWD3qxCttMgdUMdE/v6eL5FtpUCphgSDCGmdeCqPPYEOATZqUrFuJuOEEIkf9kS15EB83msUZAW9YKF/1yA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727715709; c=relaxed/simple; bh=Zq84b8AnsDyG7r8kXR1hAWw3vhewfvdG570chOh1I0U=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=fhsyQZmBOFgJce+38TLB1C4uTJrxmrRCbEfAXwZkx0SNfVWW71fC8hP92v/BpiWuiCvDqWWd4u4qICqr2tyk6VLdV5eUu9xNQ/LlM/O+fYIGjrmRNvjexqYvL6RkfSMeIqwO3cSoMYup9PPpkd4LnJpP74WZq3R93OAS5SOme14= 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=58362 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 1svJmF-008SWz-Tm; Mon, 30 Sep 2024 19:01:42 +0200 Date: Mon, 30 Sep 2024 19:01:38 +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: <87cyklm7i2.fsf@nvidia.com> X-Spam-Score: -1.9 (-) 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? Thanks.