Currently we create flows for datagrams from socket interfaces, and use
them to direct "spliced" (socket to socket) datagrams.  We don't yet
match datagrams from the tap interface to existing flows, nor create new
flows for them.  Add that functionality, matching datagrams from tap to
existing flows when they exist, or creating new ones.

As with spliced flows, when creating a new flow from tap to socket, we
create a new connected socket to receive reply datagrams attached to that
flow specifically. We extend udp_flow_sock_handler() to handle reply
packets bound for tap rather than another socket.

For non-obvious reasons (perhaps increased stack usage?), this caused
a failure for me when running under valgrind, because valgrind invoked
rt_sigreturn which is not in our seccomp filter.  Since we already
allow rt_sigaction and others in the valgrind target, it seems
reasonable to add rt_sigreturn as well.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

This implements the first steps of tracking UDP packets with the flow table
rather than its own (buggy) set of port maps.  Specifically we create flow
table entries for datagrams received from a socket (PIF_HOST or
PIF_SPLICE).

When splitting datagrams from sockets into batches, we group by the flow
as well as splicesrc.  This may result in smaller batches, but makes things
easier down the line.  We can re-optimise this later if necessary.  For now
we don't do anything else with the flow, not even match reply packets to
the same flow.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

Move all the TCP parts using internal buffers to tcp_buf.c
and keep generic TCP management functions in tcp.c.
Add tcp_internal.h to export needed functions from tcp.c and
tcp_buf.h from tcp_buf.c

With this change we can use existing TCP functions with a
different kind of memory storage as for instance the shared
memory provided by the guest via vhost-user.

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

We globally disabled this, with a justification lumped together with
several checks about braces.  They don't really go together, the others
are essentially a stylistic choice which doesn't match our style.  Omitting
brackets on macro parameters can lead to real and hard to track down bugs
if an expression is ever passed to the macro instead of a plain identifier.

We've only gotten away with the macros which trigger the warning, because
of other conventions its been unlikely to invoke them with anything other
than a simple identifier.  Fix the macros, and enable the warning for the
future.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

clang-tidy 18.1.1 in Fedora 40 complains about every #define of an integral
value, suggesting it be converted to an enum.  Although that's certainly
possible, it's of dubious value and results in some awkward arrangements on
out codebase.  Suppress it globally.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

Currently "make cppcheck" invokes cppcheck on ".", so it will check all the
.c and .h files it can find in the source tree.  This isn't ideal, because
it can find files that aren't actually part of the real build, or even
stale files which aren't in git.

More practically, some upcoming changes are looking at downloading other
source trees for some tests.  Static errors in there is Not Our Problem,
so checking them is both slow and pointless.

So, change the Makefile to invoke cppcheck only on the specific source
files that are part of the build.  For some reason in this format the
badBitmaskCheck warnings in seccomp.h which were suppressed by 5beb3472e
("cppcheck: Avoid errors due to zeroes in bitwise ORs") no longer trigger.
That means we get unmatchedSuppression warnings instead.  We add an
unmatchedSuppression suppression instead of simply removing the original
suppressions, just in case this odd behaviour isn't the same for all
cppcheck versions.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

Currently icmp_id_map[][] stores information about ping sockets in a
bespoke structure.  Move the same information into new types of flow
in the flow table.  To match that change, replace the existing ICMP
timer with a flow-based timer for expiring ping sockets.  This has the
advantage that we only need to scan the active flows, not all possible
ids.

We convert icmp_id_map[][] to point to the flow table entries, rather
than containing its own information.  We do still use that array for
locating the right ping flows, rather than using a "flow native" form
of lookup for the time being.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
[sbrivio: Update id_sock description in comment to icmp_ping_new()]
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

Introduce ip.[ch] file to encapsulate IP protocol handling functions and
structures.  Modify various files to include the new header ip.h when
it's needed.

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Message-ID: <20240303135114.1023026-5-lvivier@redhat.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

Currently port_fwd.[ch] contains helpers related to port forwarding,
particular automatic port forwarding.  We're planning to allow much more
flexible sorts of forwarding, including both port translation and NAT based
on the flow table.  This will subsume the existing port forwarding logic,
so rename port_fwd.[ch] to fwd.[ch] with matching updates to all the names
within.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

Add this helper to format an inany into either IPv4 or IPv6 text
format as appropriate.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>