[RFC] Add syslog support to boot loader

[andreasf]

When debugging without a serial port, network-based output would provide an alternative to re-typing screen output or taking pictures.

As a proof of concept this patch adds UDP-based syslog-ng support (​5424, ​RFC5426) to the boot loader. While UDP is potentially lossy, unidirectional broadcast of datagrams avoids server discovery/selection and it avoids a dependency on still-pending TCP support patches (#5240).

Output starts once the network stack is initialized - on ppc currently only when network-booting, before searching for boot volumes - and with #6166 patches until the last malloc() for kernel ELF sections.

Unfortunately this does not work in the kernel though. Linking the boot loader's network stack into the ppc kernel does work, but depending on the point of initialization either the stack initialization and sending succeed but datagrams do not arrive (e.g., in PPCPlatform::InitPostVM()), or the stack initialization's of_open() hangs as in #5160 and #4385 (e.g., in main2()).

[andreasf]

proposed patch

[andreasf]

test case: simple receiver as alternative to a real syslogd

[nielx]

Any update on this patch or this ticket?