David Goulet authored Jul 23, 2020 and Nick Mathewson committed Jul 23, 2020

Closes #40061



Signed-off-by: David Goulet <dgoulet@torproject.org>

Previously we tolerated up to 1.5 connections for every relay we
were connected to, and didn't warn if we had fewer than 5
connections total.

Now we tolerate up to 1.5 connections per relay, and up to 4
connections per authority, and we don't warn at all when we have
fewer than 25 connections total.

Fixes bug 33880, which seems to have been provoked by our #17592
change in 0.3.5.

The need for casting negative syscall arguments depends on the
glibc version. This affects the rules for the openat syscall which
uses the constant AT_FDCWD that is defined as a negative number.
This commit adds logic to only apply the cast when necessary, on
glibc versions from 2.27 onwards.

Different versions of glibc use either open or openat for the
opendir function. This commit adds logic to use the correct rule
for each glibc version, namely:
- Until 2.14 open is used
- From 2.15 to to 2.21 openat is used
- From 2.22 to 2.26 open is used
- From 2.27 onwards openat is used

The need for casting negative syscall arguments depends on the
glibc version. This affects the rules for the openat syscall which
uses the constant AT_FDCWD that is defined as a negative number.
This commit adds logic to only apply the cast when necessary, on
glibc versions from 2.27 onwards.

Our old https://bugs.torproject.org/nnnn URLs only work for bugs
numbered before 40000.  Newer gitlab bugs need to have specific
projects mentioned.

This patch assumes that bugs are in tpo/core/tor by default, but
allows us to refer to several other projects by saying
e.g. "chutney#40002" if we want.

check-cocci is still a good idea -- perhaps as a cron job?  But
doing it as part of our regular tests has just been confusing,
especially to volunteers who shouldn't have to become coccinelle
experts in order to get their patches through our CI.

Closes #40030.

Closes ticket 40035.

`-s ours` to avoid version bump.

`-s ours` to avoid version bump.

`-s ours` to avoid version bump.

`-s ours` to avoid version bump.

`-s ours` to avoid version bump.

`-s ours` to avoid version bump.

When receiving an introduction NACK, the client either decides to close or
re-extend the circuit to another intro point.

In order to do this, the service descriptor needs to exists but it is possible
that it gets removed from the cache between the establishement of the
introduction circuit and the reception of the (N)ACK.

For that reason, the BUG(desc == NULL) is removed because it is a possible
normal use case. Tor recovers gracefully already.

Fixes #34087

Signed-off-by: David Goulet <dgoulet@torproject.org>