Linux kernel udp search

Question

struct sock *udp4_lib_lookup(struct net *net, __be32 saddr, __be16 sport, __be32 daddr, __be16 dport, int dif) 

Here is a function declaration that converts connection attributes to a struct sock . Since I googled, the first argument should be &init_net . But what should be the last argument?

Answer 1

The dif argument is the device interface.