Cc'ing netfilter-devel for development questions.
On Fri, Sep 25, 2015 at 10:40:54AM +0530, Vikas wrote:
> Hi,
>
> In the netlink infra I could see these attributes:
>
> enum nfqnl_attr_type {
> 0034 NFQA_UNSPEC,0035 NFQA_PACKET_HDR,
> 0036 NFQA_VERDICT_HDR, /* nfqnl_msg_verdict_hrd */
> 0037 NFQA_MARK, /* __u32 nfmark */
> 0038 NFQA_TIMESTAMP, /* nfqnl_msg_packet_timestamp */
> 0039*NFQA_IFINDEX_INDEV*, /* __u32 ifindex */
> 0040*NFQA_IFINDEX_OUTDEV*, /* __u32 ifindex */
> 0041 NFQA_IFINDEX_PHYSINDEV, /* __u32 ifindex */
> 0042 NFQA_IFINDEX_PHYSOUTDEV, /* __u32 ifindex */
> 0043 NFQA_HWADDR, /* nfqnl_msg_packet_hw */
> 0044 NFQA_PAYLOAD, /* opaque data payload */
> 0045 NFQA_CT, /* nf_conntrack_netlink.h */
> 0046 NFQA_CT_INFO, /* enum ip_conntrack_info */
> 0047 NFQA_CAP_LEN, /* __u32 length of captured packet */
> 0048 NFQA_SKB_INFO, /* __u32 skb meta information */
> 0049 NFQA_EXP, /* nf_conntrack_netlink.h */
> 0050
> 0051 __NFQA_MAX
> 0052 };
>
> Currently we are doing this to get the input/putput interface index:
> input_interface_index = mnl_attr_get_u32(tb[NFQA_IFINDEX_INDEV]); // where tb being a nlattr structure: struct nlattr *tb[NFQA_MAX]
> output_interface_index = mnl_attr_get_u32(tb[NFQA_IFINDEX_OUTDEV]);
>
> Is there a way(or any attribute like NFQA_IFINDEX_INDEV/OUTDEV) by
> which we can get the input/output interface*name*? I don't want to
> use kernel call: if_indextoname() to map index to name, because it
> may be time consuming.
It should be easy to build a cache of ifindex in userspace and
maintain it up to date. So you don't need to use if_indextoname()
since it generates quite a lot of netlink traffic between kernel and
userspace.
You can probably contribute some example to libmnl that we can apply
to the tree. You can use this change I made quite recently as
reference for that code:
http://git.netfilter.org/nftables/commit/?id=3ed296118a065caff5600e60d4f7ef18e137f9a0
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