Add `switch_stun_packet_verify_integrity()`, an HMAC-SHA1
MESSAGE-INTEGRITY verifier that is const and non-mutating: it runs
over a private copy of the pristine network-order packet, so the
caller's buffer and byte order stay untouched, and walks attributes
with its own unsigned bounded helper `stun_wire_attr_bounds()`
instead of the host-order iterator macros. A trailing
MESSAGE-INTEGRITY-SHA256 or FINGERPRINT after MESSAGE-INTEGRITY is
tolerated; any other trailing attribute is rejected.
Gate it in `handle_ice()` behind `ice->verify_integrity`: verify
before any ICE state is touched, keyed by message type (local
`ice->pass` for a request, remote `ice->rpass` for a response or
error response), and drop on failure. Keepalive indications carry no
MESSAGE-INTEGRITY and are ignored.
`ice->verify_integrity` is read from the `ice_verify_message_integrity`
channel variable in `switch_rtp_activate_ice()` and defaults off, so
receive-path behavior is unchanged unless it is enabled. Adds unit
tests in `tests/unit/switch_stun.c`.
Route IPv6 writes in `switch_stun_packet_attribute_add_binded_address`
and `switch_stun_packet_attribute_add_xor_binded_address` through
`switch_stun_ipv6_t` (16-byte `address[]`) instead of `switch_stun_ip_t`
(4-byte `uint32_t address`).
Add IPv4/IPv6 unit tests for both encoders.
Co-authored-by: Andrey Volk <andywolk@gmail.com>
Dmitry Verenitsin