This separates out the Linux socket TCP keepalive timeout interval
from Sofia's internal mechanisms. Earlier we tied these together. In
retrospect this seems improper.
These two values can now be set separately.
You might, for example, want to keep the Sofia internal mechanism
disabled completely while enabling the platform-based mechanism if
your platform supports it.
We also here reform the default value of the socket TCP keepalive
parameter to 30 seconds.
This is what commit a0e9639a1f38f26a5dc586d386ae044ba82e0137 should
have been.
FS-6104
Sofia keeps the TCP keepalive timeout in milliseconds, but Linux
expects the value in seconds. Before this change, it's unlikely the
TCP_KEEPIDLE and TCP_KEEPINTVL calls were having much effect as we
would have been passing them a huge value.
FS-6104
This adds support for the ephemeral elliptic curve Diffie-Hellman key
exchange, which provides for forward secrecy in the event that
long-term keys are compromised.
For the moment, we've hard-coded the curve as prime256v1.
Previously there was no way to override the hard-coded cipher suite
specification of "ALL:!ADH:!LOW:!EXP:!MD5:@STRENGTH".
This commit does leave in place the hardcoded cipher spec for WebRTC
of "HIGH:!DSS:!aNULL@STRENGTH".
Previously if the TPTAG_TLS_VERSION was set to a non-zero value we
supported only TLSv1 (but not TLSv1.1 or TLSv1.2), and if was set to
zero we supported all versions of TLS and SSL (including the
ridiculous SSLv2).
Now we take an integer field where various bits can be set indicating
which versions of TLS we would like to support.
Sofia accepts a value for the TCP keepalive timeout interval via
TPTAG_KEEPALIVE, however it fails to use this value for the Linux
keepalive socket options TCP_KEEPIDLE and TCP_KEEPINTVL. In fact, on
Linux it enables the sending of TCP keepalives even if tpp_keepalive
is set to zero which would disable Sofia's internal keepalive
mechanisms. Sofia then uses a hard coded value of 30 seconds for
these keepalive intervals which affects battery life on mobile
devices.
With this commit we harmonize the sending of TCP keepalives on Linux
with other platforms by using the value from TPTAG_KEEPALIVE and not
enabling the sending of TCP keepalives at all if the value of the
parameter is zero.
FS-6104 --resolve
