Is "zero-copy networking" implemented by default on Linux?

Is "zero-copy networking" implemented by default on Linux?

I saw this article:
http://lwn.net/2001/0419/kernel.php3
Zero-copy networking will be in 2.4.4. This patch, by David Miller, Alexey
Kuznetsov, and others, has been in development and testing for some time,
and was incorporated into the "ac" kernel series back in 2.4.2ac4. In a
way, it is a surprising change to see in a stable kernel series, since it
makes fundamental changes deep in the networking code. From all reports,
however, it is solid, and, in certain situations, it should produce
significant performance benefits.
Can someone tell me if zero-copy networking exists by default in Linux, or
whether this patch was just to allow people who wanted to do zero-copy
networking to be able to implement it?
In other words, in the current Ubuntu does it perform zero-copy networking
all the time or would I have to use certain system calls to utilise the
above patch?