in_addr
in_addr stores an IP 4 internet address, i. e. 4 bytes (or 32 bits) in big endian order:
struct in_addr {
__be32 s_addr;
};
sockaddr_in
__be16 is a big endian unsigned int.
struct sockaddr_in {
__kernel_sa_family_t sin_family; /* Address family */
__be16 sin_port; /* Port number */
struct in_addr sin_addr; /* Internet address */
/* Pad to size of `struct sockaddr'. */
unsigned char __pad[__SOCK_SIZE__ - sizeof(short int) -
sizeof(unsigned short int) - sizeof(struct in_addr)];
};
The _in in sockaddr_in likely stands for internet (hence the members sin_port and sin_addr where s possibly stands for socket).