Is there a maintained alternative for libnids?

As libnids seems to be two years old and there are no current updates, do some one know any alternative solution for libnids or better library than it, as it seems to drop packets in higher speeds more than 1G/per sec

And more over it has no support for 64 bit ip addresses.

An alternative to libnids is Bro. It comes with a robust TCP reassembler which has been thoroughly tested and used by the network security monitoring community over the years. It ships with a bunch of protocol analyzers for common protocols, such as HTTP, DNS, FTP, SMTP, and SSL.

Bro is "the Python of network processing:" it has its own domain-specific scripting language with first-class types and functions for IP addresses (both v4 and v6), subnets, ports. The programming style has an asynchronous event-based flavor: users write callback functions for events that reflect network activity. The analysis operates at connection granularity. Here is an example:

event connection_established(c: connection)
{
    if ( c$id$orig_h == 1.2.3.4 && c$id$resp_p == 31337/udp )
        // IP 1.2.3.4 successfully connected to remote host at port 31337.
}

Moreover, Bro supports a cluster mode that allows for line-rate monitoring of 10 Gbps links. Because most analyses do not require sharing of inter-connection state, Bro scales very well across cores (using PF_RING) as well as multiple nodes. There exist Bro installations with >= 140 nodes. A typical deployment looks as follows:

_{(source: bro.org)}

Due to the high scalability, there is typically no more need to grapple with low-level details and fine-tune C implementations. Or put differently, with Bro you spend your time working on the analysis and not the implementation.