This duplicates a fix made to tcp.c in commit
d5735c631c.

UDP sockets can be used for multicast, at which point it becomes
plausible that we could receive packets that aren't destined for us
but that still match on a port number.

separate xfer method.

Add missing .alloc_iob entries to several xfer_interface_operations
structures.

xfer_window() function, which can return a scalar rather than a
boolean.

structures.

DHCP still broken and #if 0'd out.

present; DHCP is broken).

Achieved via Perl using:

perl -pi -e 's/pk_buff/io_buffer/g; s/Packet buffer/I\/O buffer/ig; ' \
	-e 's/pkbuff\.h/iobuf.h/g; s/pkb_/iob_/g; s/_pkb/_iob/g; ' \
	-e 's/pkb/iobuf/g; s/PKB/IOB/g;'

connections might break things. Only-sending applications like syslog()
do not need a newdata() handler, so added a check if that handler exists.

it as a fallback network device rather than an explicitly forced network
device.

Clear routing table entries before re-attempting DHCP.

udp_senddata() callback.  This will simplify any UDP protocols that don't
need the temporary buffer.

to set up dummy routing entries.

transmissions.

skb_tailroom().  Add pkb_headroom().

Simplify checksum generation on the TX datapath.

defined in vsprintf.h.  (This may change, since vsprintf.h is a
non-standard name, but for now it's the one to use.)

There should be no need to include vsprintf.h just for DBG() statements,
since include/compiler.h forces it in for a debug build anyway.

Added a large number of missing calls to free_pkb().  In the case of UDP,
no received packets were ever freed, which lead to memory exhaustion
remarkably quickly once pxelinux started up.

In general, any function with _rx() in its name which accepts a pk_buff
*must* either call free_pkb() or pass the pkb to another _rx() function
(e.g. the next layer up the stack).  Since the UDP (and TCP) layers don't
pass packet buffers up to the higher-layer protocols (the
"applications"), they must free the packet buffer after calling the
application's newdata() method.

udp_connect() now follows the standard BSD sockets semantics and simply
sets the default address for outgoing packets; it doesn't filter incoming
packets.

Updated PXE API dispatcher to use copy_{to,from}_user, and moved to
arch/i386 since the implementation is quite architecture-dependent.
(The individual PXE API calls can be largely
architecture-independent.)

Introduced struct sockaddr_tcpip, to simplify code that deals with
both IPv4 and IPv6 addresses.

Reorganised parts of tcpip.c and udp.c.

the TCP/IP protocol suite (rather than being general transport-layer
functions).

if the application wants to send data then it will have to use the normal
senddata() mechanism.

against value in header.

Temporarily disable RX checksumming; it's broken and is holding up
work on higher-layer protocols
.

a pointer).

Use pkb_available() rather than pkb_len() (which will always return 0
on a freshly allocated buffer).

udp_send() should assume that the buffer has already been allocated.

1. Updated UDP send data code\
2. Corrected internet checksum\
3. Moved udp_buffer() and udp_buflen() to udp.c from udp.h