nf_queue claims to support copy size of up to 0xffff:
case NFQNL_COPY_PACKET:
/* we're using struct nlattr which has 16bit nla_len */
if (range > 0xffff)
queue->copy_range = 0xffff;
Which is incorrect, as the maximum attribute size is 0xffff - NLA_HDRLEN.
Thus, when trying to queue a maximum-sized IP packet, you get
NFQA_PAYLOAD with nla->len = 4 (due to overflow), i.e. no payload at
all.
Since this is a limitation of netlink this isn't fixable in nfqueue.
How to best handle this situation?
We can either truncate and queue 0xffff - NLA_HDRLEN (i.e., cut off 4
bytes from what will be queued), or we could refuse to queue the packet
(userspace asked for the full packet, but we can't fullfill the
request).
Any ideas/suggestions?
Thanks,
Florian
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