Add iSCSI boot support

[andreasf]

iSCSI is a TCP-based protocol for accessing Network Attached Storage.

On a Solaris host for instance, a disk image can be set up as iSCSI target by a one-liner:

iscsitadm create target --backing-store path/to/generated/haiku.image haiku-ppc

Discovery sessions allow to list all targets served by a host, such as the TFTP server.

In normal sessions, regular SCSI commands are used to transfer data.

[andreasf]

patch

[andreasf]

The attached patch moves my parse_ip_address function around, so that it can be used for iSCSI, beyond Open Firmware.

Please apply this part.

[andreasf]

draft patch

[andreasf]

Code is Big Endian only for now.

Discovery is implemented, attempting to connect to each IPv4 TargetAddress, ignoring setups with multiple Target Portal Groups for now.

Basic session login and logout is implemented. The volume size is apparently read correctly.

Reading actual data is not yet working. There is an unexpected (stray?) SCSI response of type CHECK CONDITION.

Adding the discovered disk Node to the NodeList didn't work from inside the iSCSI code, so I needed to add a callback for it to link. This may be connected to _BOOT_MODE not being defined for the boot_net library, leading to an undefined reference dprintf_no_syslog.

[axeld]

ip_parse_address() patch applied in hrev35522, thanks, and sorry for the long delay!

[andreasf]

Applied slightly differently in hrev38528, hrev38535 and hrev38536.