Allow users to specify multiple dump configurations in a prioritized list.
This enables fallback to secondary device(s) if primary dump fails. E.g.,
one might configure a preference for netdump, but fallback to disk dump as a
second choice if netdump is unavailable.
This change does not list-ify netdump configuration, which is tracked
separately from ordinary disk dumps internally; only one netdump
configuration can be made at a time, for now. It also does not implement
IPv6 netdump.
savecore(8) is already capable of scanning and iterating multiple devices
from /etc/fstab or passed on the command line.
This change doesn't update the rc or loader variables 'dumpdev' in any way;
it can still be set to configure a single dump device, and rc.d/savecore
still uses it as a single device. Only dumpon(8) is updated to be able to
configure the more complicated configurations for now.
As part of revving the ABI, unify netdump and disk dump configuration ioctl
/ structure, and leave room for ipv6 netdump as a future possibility.
Backwards-compatibility ioctls are added to smooth ABI transition,
especially for developers who may not keep kernel and userspace perfectly
synced.
Reviewed by: markj, scottl (earlier version)
Relnotes: maybe
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D19996
This is a component of a system which lets the kernel dump core to
a remote host after a panic, rather than to a local storage device.
The server component is available in the ports tree. netdump is
particularly useful on diskless systems.
The netdump(4) man page contains some details describing the protocol.
Support for configuring netdump will be added to dumpon(8) in a future
commit. To use netdump, the kernel must have been compiled with the
NETDUMP option.
The initial revision of netdump was written by Darrell Anderson and
was integrated into Sandvine's OS, from which this version was derived.
Reviewed by: bdrewery, cem (earlier versions), julian, sbruno
MFC after: 1 month
X-MFC note: use a spare field in struct ifnet
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D15253
