Question

The linux/ folder contains the ip.h header file, wherein part of the structure of IP header is defined as follows:

struct iphdr
{
     // ...
     __be32 saddr;
     __be32 daddr;
};

I have a situation wherein I have a source netmask of type char*. I want to check whether a IP address of type __be32 belongs to a network with address of type char*. I can convert netmask and network address to __be32 using in_aton() provided in linux/inet.h.

 char * network_addr = "192.166.0.0";
 char * netmask = "255.255.0.0";

Can someone please tell how can I take the boolean && of addresses being type __be32 or just applying && operator will give correct result.

Thanks.

Answer 1

You are looking for the bitwise AND operator & and not the logical AND operator &&:

__be32 addr;
__be32 addr_mask;
...
__be32 addr_masked = addr & addr_mask;

Remember IPv4 adresses are 32-bit number: 4 x 8-bit bytes