[Bridge] [PATCH] netfilter: nft_meta: fix bridge port vlan ID selector

[Nikolay Aleksandrov]

On 03/07/2019 15:48, Nikolay Aleksandrov wrote:
> On 03/07/2019 15:40, Pablo Neira Ayuso wrote:
>> Use br_vlan_enabled() and br_vlan_get_pvid() helpers as Nikolay
>> suggests.
>>
>> Rename NFT_META_BRI_PVID to NFT_META_BRI_IIFPVID before this patch hits
>> the 5.3 release cycle, to leave room for matching for the output bridge
>> port in the future.
>>
>> Reported-by: Nikolay Aleksandrov <nikolay at cumulusnetworks.com>
>> Fixes: da4f10a4265b ("netfilter: nft_meta: add NFT_META_BRI_PVID support")
>> Signed-off-by: Pablo Neira Ayuso <pablo at netfilter.org>
>> ---
>>  include/uapi/linux/netfilter/nf_tables.h |  4 ++--
>>  net/netfilter/nft_meta.c                 | 17 ++++++++++-------
>>  2 files changed, 12 insertions(+), 9 deletions(-)
>>
> 
> Ah actually I might've hurried too much with the suggestion, we don't have a helper to
> check through a port if vlan filtering has been enabled. The helper assumes that
> the device is a bridge. So below you'll have to use p->br->dev with br_vlan_enabled().
> And in fact the proper way would be to get the "upper" device via netdev_master_upper_dev_get()
> and then to use that in order to avoid direct dereferencing.
> 

Sorry for the multiple replies, I just noticed this is running from fast-path so you'll
have to use the _rcu variant and check for null since they are unlinked before the port
flag is removed in del_nbp() (bridge/bf_if.c).

>> diff --git a/include/uapi/linux/netfilter/nf_tables.h b/include/uapi/linux/netfilter/nf_tables.h
>> index 8859535031e2..8a1bd0b1ec8c 100644
>> --- a/include/uapi/linux/netfilter/nf_tables.h
>> +++ b/include/uapi/linux/netfilter/nf_tables.h
>> @@ -795,7 +795,7 @@ enum nft_exthdr_attributes {
>>   * @NFT_META_SECPATH: boolean, secpath_exists (!!skb->sp)
>>   * @NFT_META_IIFKIND: packet input interface kind name (dev->rtnl_link_ops->kind)
>>   * @NFT_META_OIFKIND: packet output interface kind name (dev->rtnl_link_ops->kind)
>> - * @NFT_META_BRI_PVID: packet input bridge port pvid
>> + * @NFT_META_BRI_IIFPVID: packet input bridge port pvid
>>   */
>>  enum nft_meta_keys {
>>  	NFT_META_LEN,
>> @@ -826,7 +826,7 @@ enum nft_meta_keys {
>>  	NFT_META_SECPATH,
>>  	NFT_META_IIFKIND,
>>  	NFT_META_OIFKIND,
>> -	NFT_META_BRI_PVID,
>> +	NFT_META_BRI_IIFPVID,
>>  };
>>  
>>  /**
>> diff --git a/net/netfilter/nft_meta.c b/net/netfilter/nft_meta.c
>> index 4f8116de70f8..b8d8adc0852e 100644
>> --- a/net/netfilter/nft_meta.c
>> +++ b/net/netfilter/nft_meta.c
>> @@ -240,14 +240,17 @@ void nft_meta_get_eval(const struct nft_expr *expr,
>>  			goto err;
>>  		strncpy((char *)dest, p->br->dev->name, IFNAMSIZ);
>>  		return;
>> -	case NFT_META_BRI_PVID:
>> +	case NFT_META_BRI_IIFPVID: {
>> +		u16 p_pvid;
>> +
>>  		if (in == NULL || (p = br_port_get_rtnl_rcu(in)) == NULL)
>>  			goto err;
>> -		if (br_opt_get(p->br, BROPT_VLAN_ENABLED)) {
>> -			nft_reg_store16(dest, br_get_pvid(nbp_vlan_group_rcu(p)));
>> -			return;
>> -		}
>> -		goto err;
>> +		if (!br_vlan_enabled(in))
>> +			goto err;
>> +		br_vlan_get_pvid(in, &p_pvid);
>> +		nft_reg_store16(dest, p_pvid);
>> +		return;
>> +	}
>>  #endif
>>  	case NFT_META_IIFKIND:
>>  		if (in == NULL || in->rtnl_link_ops == NULL)
>> @@ -375,7 +378,7 @@ static int nft_meta_get_init(const struct nft_ctx *ctx,
>>  			return -EOPNOTSUPP;
>>  		len = IFNAMSIZ;
>>  		break;
>> -	case NFT_META_BRI_PVID:
>> +	case NFT_META_BRI_IIFPVID:
>>  		if (ctx->family != NFPROTO_BRIDGE)
>>  			return -EOPNOTSUPP;
>>  		len = sizeof(u16);
>>
>