structre object question

Hello,
In linux kernel source etheernet header is defined as structure as
struct ethhdr
{
unsigned char h_dest[ETH_ALEN]; /* destination eth addr */
unsigned char h_source[ETH_ALEN]; /* source ether addr */
unsigned short h_proto; /* packet type ID field */
} __attribute__((packed));
I want to know what __attribute__((packed)) meance?
It is not looking as a structure object then what is thati?
regards,
cranium

kernel.lover wrote:
> Hello,
> In linux kernel source etheernet header is defined as structure as
> struct ethhdr
> {
> unsigned char h_dest[ETH_ALEN]; /* destination eth addr */
> unsigned char h_source[ETH_ALEN]; /* source ether addr */
> unsigned short h_proto; /* packet type ID field */
> } __attribute__((packed));
> I want to know what __attribute__((packed)) meance?
> It is not looking as a structure object then what is thati?
> regards,
> cranium

Sometimes google is your friend.

http://www.google.com/search?hl=en&q...=Google+Search

searched for 'gcc packed'. Top link should help some, there are more...

"kernel.lover" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) om...
> Hello,
> In linux kernel source etheernet header is defined as structure as
> struct ethhdr
> {
> unsigned char h_dest[ETH_ALEN]; /* destination eth addr */
> unsigned char h_source[ETH_ALEN]; /* source ether addr */
> unsigned short h_proto; /* packet type ID field */
> } __attribute__((packed));
> I want to know what __attribute__((packed)) meance?
> It is not looking as a structure object then what is thati?
> regards,
> cranium

__attribute__((packed)) is used for different OS when sending messages.
For example:
If your ethhdr is 15 bytes, if you do not use the flag, local machine
will full fill the package to 16 bytes, and remote machine may be conflict
with it.
If you use flag __attribute__((packed)), the system will not fill the
space and the package only be sent with 15 bytes.