docs/designs/sol-sysrq.md

12 low-level commands. BMC usually provides SysRq support in KVM and SOL functions,
13 but this is not available in OpenBMC. This doc is to provide the SysRq support
19 another key, which controls the command issued. This is not typical key code and
31 - The ipmitool SOL.
32 - The SOL in WebUI.
33 - The console with SSH (default) 2200 port.
37 In OpenBMC, the service `obmc-console-server` provides the host console and
41 sequence `\n~B` is used to send the "break signal" between clients and
42 console-server. In `obmc-console`, a state machine shall handle the sequence.
43 Once the sequence is detected, it could invoke `tcsendbreak()` to send the
48 In `phosphor-ipmi-net`, the code in `processInboundPayload()` shall handle the
49 break signal from ipmitool, and send the sequence `\n~B` to the server.
60 ### obmc-console
62 As the obmc-console server, in `console-server.h`, a simple state machine is
66 ---
68 ---
69 stateDiagram-v2
70     [*] --> Empty
71     Empty --> Emit: [^#92;n]
72     Emit --> [*]
73     Empty --> Newline: [#92;n]
74     Newline --> Escape: [~]
75     Newline --> EmitNewline: [^#92;n]
76     Escape --> EmitEscapeCode: [B]
77     EmitEscapeCode --> [*]
78     EmitNewline --> [*]
79     Escape --> EmitNewlineTilde: [^B]
80     EmitNewlineTilde --> [*]
83 If `EmitEscapeCode` state is reached, it shall call `tcsendbreak()` to send the
88 An alternative way to send the "break signal" between clients and console-server
91 modified to send `MSG_OOB` to obmc-console when the user enter the key code
92 sequence `\n~B`. When obmc-console receive `MSG_OOB`, it shall send the "break
95 However, in this solution, in some scenarios, obmc-console can not handle the
98 [sockatmark(3)][5]. But it requires signalling the `MSG_OOB` in all obmc-console
105 - netipmid
106 - obmc-console
112 sequence `\n~~B`, the first tilde will be processed by obmc-console-client, the
113 second tilde will reach obmc-console-server.
116 [2]: https://www.kernel.org/doc/html/latest/admin-guide/sysrq.html
117 [3]: https://github.com/ipmitool/ipmitool/blob/master/lib/ipmi_sol.c#L1398-L1401
119   https://github.com/openbmc/phosphor-net-ipmid/commit/ec4374146147e339132243725d345eb30ec2da1d
120 [5]: https://man7.org/linux/man-pages/man3/sockatmark.3.html