17.9 Routing Table Operations
On some systems, two ioctl requests are
provided to operate on the routing table. These two requests
require that the third argument to ioctl be a pointer to
an rtentry structure, which is defined by including the
<net/route.h> header. These requests are normally
issued by the route program. Only the superuser can issue
these requests. On systems with routing sockets (Chapter 18), these requests
use routing sockets instead of ioctl.
SIOCADDRT
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Add an entry to the routing table.
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SIOCDELRT
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Delete an entry from the routing table.
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There is no way with ioctl to list all
the entries in the routing table. This operation is usually
performed by the netstat program when invoked with the
-r flag. This program obtains the routing table by reading
the kernel's memory (/dev/kmem). As with listing the ARP
cache, we will see an easier (and better) way to do this using
sysctl in Section 18.4.
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