netdev - Re: [PATCH net-next 9/9] netfilter: nf_tables: add support to destroy operation

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Date:   Fri, 20 Jan 2023 10:58:53 +0100
From:   "Fernando F. Mancera" <ffmancera@...eup.net>
To:     Vlad Buslov <vladbu@...dia.com>, Florian Westphal <fw@...len.de>
Cc:     netdev@...r.kernel.org, Jakub Kicinski <kuba@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        netfilter-devel@...r.kernel.org,
        Pablo Neira Ayuso <pablo@...filter.org>,
        Maor Dickman <maord@...dia.com>
Subject: Re: [PATCH net-next 9/9] netfilter: nf_tables: add support to destroy
 operation

Hi Vlad,

On 19/01/2023 08:29, Vlad Buslov wrote:
> On Wed 18 Jan 2023 at 13:32, Florian Westphal <fw@...len.de> wrote:
>> From: Fernando Fernandez Mancera <ffmancera@...eup.net>
>>
>> Introduce NFT_MSG_DESTROY* message type. The destroy operation performs a
>> delete operation but ignoring the ENOENT errors.
>>
>> This is useful for the transaction semantics, where failing to delete an
>> object which does not exist results in aborting the transaction.
>>
>> This new command allows the transaction to proceed in case the object
>> does not exist.
>>
>> Signed-off-by: Fernando Fernandez Mancera <ffmancera@...eup.net>
>> Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
>> Signed-off-by: Florian Westphal <fw@...len.de>
>> ---
>>   include/uapi/linux/netfilter/nf_tables.h |  14 +++
>>   net/netfilter/nf_tables_api.c            | 111 +++++++++++++++++++++--
>>   2 files changed, 117 insertions(+), 8 deletions(-)
>>
>> diff --git a/include/uapi/linux/netfilter/nf_tables.h b/include/uapi/linux/netfilter/nf_tables.h
>> index cfa844da1ce6..ff677f3a6cad 100644
>> --- a/include/uapi/linux/netfilter/nf_tables.h
>> +++ b/include/uapi/linux/netfilter/nf_tables.h
>> @@ -98,6 +98,13 @@ enum nft_verdicts {
>>    * @NFT_MSG_GETFLOWTABLE: get flow table (enum nft_flowtable_attributes)
>>    * @NFT_MSG_DELFLOWTABLE: delete flow table (enum nft_flowtable_attributes)
>>    * @NFT_MSG_GETRULE_RESET: get rules and reset stateful expressions (enum nft_obj_attributes)
>> + * @NFT_MSG_DESTROYTABLE: destroy a table (enum nft_table_attributes)
>> + * @NFT_MSG_DESTROYCHAIN: destroy a chain (enum nft_chain_attributes)
>> + * @NFT_MSG_DESTROYRULE: destroy a rule (enum nft_rule_attributes)
>> + * @NFT_MSG_DESTROYSET: destroy a set (enum nft_set_attributes)
>> + * @NFT_MSG_DESTROYSETELEM: destroy a set element (enum nft_set_elem_attributes)
>> + * @NFT_MSG_DESTROYOBJ: destroy a stateful object (enum nft_object_attributes)
>> + * @NFT_MSG_DESTROYFLOWTABLE: destroy flow table (enum nft_flowtable_attributes)
>>    */
>>   enum nf_tables_msg_types {
>>   	NFT_MSG_NEWTABLE,
>> @@ -126,6 +133,13 @@ enum nf_tables_msg_types {
>>   	NFT_MSG_GETFLOWTABLE,
>>   	NFT_MSG_DELFLOWTABLE,
>>   	NFT_MSG_GETRULE_RESET,
>> +	NFT_MSG_DESTROYTABLE,
>> +	NFT_MSG_DESTROYCHAIN,
>> +	NFT_MSG_DESTROYRULE,
>> +	NFT_MSG_DESTROYSET,
>> +	NFT_MSG_DESTROYSETELEM,
>> +	NFT_MSG_DESTROYOBJ,
>> +	NFT_MSG_DESTROYFLOWTABLE,
>>   	NFT_MSG_MAX,
>>   };
>>   
>> diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
>> index 8c09e4d12ac1..974b95dece1d 100644
>> --- a/net/netfilter/nf_tables_api.c
>> +++ b/net/netfilter/nf_tables_api.c
>> @@ -1401,6 +1401,10 @@ static int nf_tables_deltable(struct sk_buff *skb, const struct nfnl_info *info,
>>   	}
>>   
>>   	if (IS_ERR(table)) {
>> +		if (PTR_ERR(table) == -ENOENT &&
>> +		    NFNL_MSG_TYPE(info->nlh->nlmsg_type) == NFT_MSG_DESTROYTABLE)
>> +			return 0;
>> +
>>   		NL_SET_BAD_ATTR(extack, attr);
>>   		return PTR_ERR(table);
>>   	}
>> @@ -2639,6 +2643,10 @@ static int nf_tables_delchain(struct sk_buff *skb, const struct nfnl_info *info,
>>   		chain = nft_chain_lookup(net, table, attr, genmask);
>>   	}
>>   	if (IS_ERR(chain)) {
>> +		if (PTR_ERR(chain) == -ENOENT &&
>> +		    NFNL_MSG_TYPE(info->nlh->nlmsg_type) == NFT_MSG_DESTROYCHAIN)
>> +			return 0;
>> +
>>   		NL_SET_BAD_ATTR(extack, attr);
>>   		return PTR_ERR(chain);
>>   	}
>> @@ -3716,6 +3724,10 @@ static int nf_tables_delrule(struct sk_buff *skb, const struct nfnl_info *info,
>>   		chain = nft_chain_lookup(net, table, nla[NFTA_RULE_CHAIN],
>>   					 genmask);
>>   		if (IS_ERR(chain)) {
>> +			if (PTR_ERR(rule) == -ENOENT &&
> 
> Coverity complains that at this point rule is not initialized yet, which
> looks like to be the case to me.
> 

Thanks, I am sending a patch fixing this.

> [...]
>