UDP internals

Low-level functions mostly internal to the UDP driver. More...

Functions
ushort	udpChksum (struct packet *pkt, ushort len, const struct netaddr *src, const struct netaddr *dst)
struct udp *	udpDemux (ushort dstpt, ushort srcpt, const struct netaddr *dstip, const struct netaddr *srcip)
syscall	udpFreebuf (struct udpPkt *udppkt)
struct udpPkt *	udpGetbuf (struct udp *udpptr)
syscall	udpRecv (struct packet *pkt, const struct netaddr *src, const struct netaddr *dst)
syscall	udpSend (struct udp *udpptr, ushort datalen, const void *buf)

Detailed Description

Low-level functions mostly internal to the UDP driver.

Function Documentation

ushort udpChksum	(	struct packet *	pkt,
		ushort	len,
		const struct netaddr *	src,
		const struct netaddr *	dst
	)

Calculate the checksum of a UDP packet based on UDP and IP information

Parameters

udppkt	UDP packet to calculate checksum for
len	Length of UDP packet
src	Source IP Address
dst	Destination IP Address

Returns

The checksum of the UDP packet

struct udp* udpDemux	(	ushort	dstpt,
		ushort	srcpt,
		const struct netaddr *	dstip,
		const struct netaddr *	srcip
	)

Locate the UDP socket for a UDP packet

Parameters

dstpt	destination port of the UDP packet
srcpt	source port of the UDP packet
dstip	destination IP of the UDP packet
srcip	source IP of the UDP packet

Returns

most completely matched socket, NULL if no match

Precondition

-condition interrupts are already disabled

Postcondition

-condition interrupts are still disabled

syscall udpRecv	(	struct packet *	pkt,
		const struct netaddr *	src,
		const struct netaddr *	dst
	)

Receive a UDP packet and place it in the UDP device's input buffer

Parameters

pkt	Incoming UDP packet
src	Source address
dst	Destination address

Returns

OK if UDP packet is received properly, otherwise SYSERR

syscall udpSend	(	struct udp *	udpptr,
		ushort	datalen,
		const void *	buf
	)

Send a UDP packet through a UDP device, thereby sending it over the network with the address/port parameters with which the UDP device is configured.

This function is intended to be internal to the UDP code. From external code use write(), which calls udpWrite().

Note: depending on the lower levels of the network stack, this function likely only buffers the packet to be sent at some later time. Therefore, it may not have actually been transmitted on the wire when this function returns.

The UDP device MUST be open and MUST remain open throughout the execution of this function.

Parameters

udpptr	Pointer to the control block for the UDP device.
datalen	Number of bytes of data to send, which must be a valid value for the current UDP device mode (e.g. if in passive mode, it must be at least the length of the UDP pseudo-header plus UDP header).
buf	Buffer of data to send. In the default mode, this will interpreted as the UDP payload; however, if the UDP device is in passive mode, this will interpreted as the UDP pseudo-header follewed by the UDP header followed by the UDP payload.

Returns

OK if packet was sent successfully; otherwise SYSERR or an error code returned by ipv4Send().