From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: IP header identification field is zero, why?
Date: Thu, 08 Oct 2009 11:18:28 +0200
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Cc: netdev@vger.kernel.org
To: thomas yang <lampsu@gmail.com>
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thomas yang a =E9crit :

> The IP ID for TCP is non-zero, but for UDP is zero,  strange.
>=20
> I want to make the IP ID (not always zero) for UDP packets, what shou=
ld I do?
> (I want to use 'IP header ID, flags, offset, protocol' to identify an
> IP packets)

As I said, you can connect() your udp socket, if you send/receive trafi=
c to/from a given destination.

if (connected_sock)
	res =3D connect(sock, (struct sockaddr *)&addr, sizeof(addr));

(Only once)


Then, your sendto() can be faster (because no route lookup is performed=
)

   if (sendto(sock, buffer, psize, 0,
                  connected_socks ? NULL : (struct sockaddr *)&addr,
                                   sizeof(struct sockaddr_in)) !=3D -1)

Then linux *will* generate an ID for each datagram.