the use sin_zero in sockaddr_in

Hi all,

Could anyone please explain the use *sin_zero in *sockaddr_in?

struct sockaddr_in{
short sin_family; /* AF_INET */
u_short sin_port; /* 16-bit port number */
/* network byte ordered */
struct in_addr sin_addr; /* 32-bit netid/hostid */
/* network byte ordered */
* char sin_zero[8]; /* unused */*
}

Thanks,
Prabhu

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Padding to allow for casting.

Jose Celestino | http://japc.uncovering.org/files/japc-pgpkey.asc
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"Assumption is the Mother of Screw-Up" -- Mr. John Elwood Hale

Hi Jose,

Could u please elaborate little more... why we need this 8 byte padding.

My complete Question:
1. Actually total size of sockaddr_in is 16 byte and out of 16 byte why we have to use 8 byte for padding.?
2. Do we use these 8 byte for any other usage for real time?

Thanks,
Prabhu

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Unix network programming chapter 3.2 says that, "The POSIX specification requires
only three members in the structure: sin_family, sin_addr, and sin_port. It is acceptable for a POSIX-compliant implementation to define additional structure members, and this is normal for an Internet socket address structure. Almost all implementations add the sin_zero member so that all socket address structures are at least 16 bytes in size. "

It's kinda like structure padding, maybe reserved for extra fields in the future. You will never use it, just as commented.

Wick
MSN/GTalk: izhangxc[AT]gmail.com

Unix network programming chapter 3.2 says that, "The POSIX specification requires only three members in the structure: sin_family, sin_addr, and sin_port. It is acceptable for a POSIX-compliant implementation to define additional structure members, and this is normal for an Internet socket address structure. Almost all implementations add the sin_zero member so that all socket address structures are at least 16 bytes in size. "

It's kinda like structure padding, maybe reserved for extra fields in the future. You will never use it, just as commented.