<snip>
IETF STD5 about the IP protocol itself specifically states that the source
route option is used by gateways (and not only by end node):
on page 18:
The loose source and record route (LSRR) option provides a means
for the source of an internet datagram to supply routing
information to be used by the gateways in forwarding the
datagram to the destination, and to record the route
information.
and later on page 21:
When an internet module routes a datagram it checks to see if
the record route option is present. If it is, it inserts its
own internet address as known in the environment into which this
datagram is being forwarded into the recorded route begining at
the octet indicated by the pointer, and increments the pointer
by four.
<end snip>
My understanding of this is that all routers MUST have a look at the
IPv4 options if LSRR is available, and this is different with IPv6.