tcp: allow SOL_SOCKET level socket options via sysctl interface

[tuexen]

Summary

When setting a SOL_SOCKET-level socket option, the TCP handler refers to the IP handler, which only handles SO_SETFIB and SO_MAX_PACING_RATE. So call sosetopt(), which handles all SOL_SOCKET-level options.
We could call sosetopt() always, but that would do a INP_WUNLOCK() followed up by a INP_WLOCK() in cases where the level is not SOL_SOCKET.

[rscheff]

Since this is from tcpsso - just curious if it wouldn't be possible to call setsockopt from within that utility after getting the socket from the inpcb id?

[tuexen]

In D42985#979996, @rscheff wrote:

Since this is from tcpsso - just curious if it wouldn't be possible to call setsockopt from within that utility after getting the socket from the inpcb id?

tcpsso does not get the socket. It is the kernel in sysctl_setsockopt(), which can access the socket. It already does so to add a reference to it.

[rscheff]

So, no way to change the e.g. SO_SNDBUF on existing kernels then.. :(

[tuexen]

In D42985#980016, @rscheff wrote:

So, no way to change the e.g. SO_SNDBUF on existing kernels then.. :(

No, but you know which patch to apply...