This implements flow preparation on the source, transfer of data with
a format roughly inspired by struct tcp_tap_conn, plus a specific
structure for parameters that don't fit in the flow table, and flow
insertion on the target, with all the appropriate window options,
window scaling, MSS, etc.

Contents of pending queues are transferred as well.

The target side is rather convoluted because we first need to create
sockets and switch them to repair mode, before we can apply options
that are *not* stored in the flow table. This also means that, if
we're testing this on the same machine, in the same namespace, we need
to close the listening socket on the source before we can start moving
data.

Further, we need to connect() the socket on the target before we can
restore data queues, but we can't do that (again, on the same machine)
as long as the matching source socket is open, which implies an
arbitrary limit on queue sizes we can transfer, because we can only
dump pending queues on the source as long as the socket is open, of
course.

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

This doesn't actually belong to passt's own policy: we should export
an interface and libvirt's policy should use it, because passt's
policy shouldn't be aware of svirt_image_t at all.

However, libvirt doesn't maintain its own policy, which makes policy
updates rather involved. Add this workaround to ensure --vhost-user
is working in combination with libvirt, as it might take ages before
we can get the proper rule in libvirt's policy.

Reported-by: Laine Stump <laine@redhat.com>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

...other than being convenient, they might be reasonably
representative of typical stand-alone usage.

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

If libvirtd is triggered by an unprivileged user, the virt-aa-helper
mechanism doesn't work, because per-VM profiles can't be instantiated,
and as a result libvirtd runs unconfined.

This means passt can't start, because the passt subprofile from
libvirt's profile is not loaded either.

Example:

  $ virsh start alpine
  error: Failed to start domain 'alpine'
  error: internal error: Child process (passt --one-off --socket /run/user/1000/libvirt/qemu/run/passt/1-alpine-net0.socket --pid /run/user/1000/libvirt/qemu/run/passt/1-alpine-net0-passt.pid --tcp-ports 40922:2) unexpected fatal signal 11

Add an annoying workaround for the moment being. Much better than
encouraging users to start guests as root, or to disable AppArmor
altogether.

Reported-by: Prafulla Giri <prafulla.giri@protonmail.com>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

A privileged helper to set/clear TCP_REPAIR on sockets on behalf of
passt. Not used yet.

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

On Fedora 41, without "allow pasta_t unconfined_t:dir read"
/usr/bin/pasta can't open /proc/[pid]/ns, which is required by
pasta_netns_quit_init().

This patch also remove one duplicate rule "allow pasta_t nsfs_t:file
read;", "allow pasta_t nsfs_t:file { open read };" at line 123 is
enough.

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

If passt or pasta are started as root, we need to read the passwd file
(be it /etc/passwd or whatever sssd provides) to find out UID and GID
of 'nobody' so that we can switch to it.

Instead of a bunch of allow rules for passwd_file_t and sssd macros,
use the more convenient auth_read_passwd() interface which should
cover our usage of getpwnam().

The existing rules weren't actually enough:

  # strace -e openat passt -f
  [...]
  Started as root, will change to nobody.
  openat(AT_FDCWD, "/etc/nsswitch.conf", O_RDONLY|O_CLOEXEC) = 4
  openat(AT_FDCWD, "/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 4
  openat(AT_FDCWD, "/lib64/libnss_sss.so.2", O_RDONLY|O_CLOEXEC) = 4
  openat(AT_FDCWD, "/var/lib/sss/mc/passwd", O_RDONLY|O_CLOEXEC) = -1 EACCES (Permission denied)
  openat(AT_FDCWD, "/var/lib/sss/mc/passwd", O_RDONLY|O_CLOEXEC) = -1 EACCES (Permission denied)
  openat(AT_FDCWD, "/etc/passwd", O_RDONLY|O_CLOEXEC) = 4

with corresponding SELinux warnings logged in audit.log.

Reported-by: Minxi Hou <mhou@redhat.com>
Analysed-by: Miloš Malik <mmalik@redhat.com>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

...for both passt and pasta: use passt's abstraction for this.

Fixes: eedc81b6ef55 ("fwd, conf: Probe host's ephemeral ports")
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

Since commit eedc81b6ef55 ("fwd, conf: Probe host's ephemeral ports"),
we might need to read from /proc/sys/net/ipv4/ip_local_port_range in
both passt and pasta.

While pasta was already allowed to open and write /proc/sys/net
entries, read access was missing in SELinux's type enforcement: add
that.

In passt, instead, this is the first time we need to access an entry
there: add everything we need.

Fixes: eedc81b6ef55 ("fwd, conf: Probe host's ephemeral ports")
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

...instead of the latest author for contrib/fedora.

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