This enum is neither IPv4-specific, nor does it
have to do anything with the network layer, as the
name may imply. The enum is moved to a new header
containing common IPv4/IPv6 definitions.

Commit ad73ade needlessly introduced an IPv4 directory.
If we were to keep it, sharing common headers between IPv4 and IPv6
would be much messier, and may potentially increase code duplication.

This change renames the IPv4 directory to IP to aid with later IPv6
porting efforts.

Up until now, the internet_checksum function lived in IPv4.h. Due to
its use in IPv6, a better place for it nowadays would be in IP.h.

Due to how it gets used in IPv6 scenarios, it makes sense to extend it
to run over multiple smaller structs instead of one big continous chunk
of memory. This change converts internet_checksum into a class with
methods "add" and "finish", which process data and return the final
result, respectively.

This commit also fixes proper hash computation for payloads that have
an odd length. Furthermore, the function was refactored to use
a ReadonlyBytes object instead of separate data and size.

Co-Authored-By: Wanda <[email protected]>

Up until now, protocol handlers for IPv4 and ARP had to rediscover the
adapter based on trying to match the address to all interfaces. This
approach is relatively slow, introduces more code duplication, and
doesn't work with multiple IPs per interface (as is the case with
IPv6).

This change introduces directly passing the adapter to all handlers
that need it, cutting out the retrieval process. Furthermore, we
discard the packet much faster if the IP doesn't match.

This commit introduces the first bit of IPv6 support into
SerenityOS. An IPv6 packet header structure allows NetworkTask to
recognize and log correctly shaped IPv6 packets, but nothing is done
with those yet. A new logging flag, IPV6_DEBUG, allows debugging of
IPv6 internals.

Co-Authored-By: sdomi <[email protected]>

This change also migrates the existing fill_in_ipv4_header from C-style
casts to proper C++ casts.

This commit adds the minimum amount of code to make Serenity reply to
ICMPv6 ping packets. This includes basic Network Discovery Protocol
support, as well as a basic ICMPv6 Echo Request/Response handler.

This change also introduces a new debug flag, ICMPV6_DEBUG.

Co-Authored-By: kleines Filmröllchen <[email protected]>

According to ARP.h, address lengths default to size of their
underlying types (IPv4Address and MACAddress respectively). We never
modify those values, and in reality, ARP never carries anything else.
Hence, those checks resolved to comparing sizeof to itself, which
probably gets optimized out of the compiler anyways.

This change removes the checks that will never fail, plus changes the
function definition to pass adapter directly, matching other handlers.

Unifying with other structures, this introduces m_payload for all
relevant structures, except the TCP header (which has a different
concept of payload than the rest).

This allows us to return a pointer directly instead of doing pointer
arithmetic to point to the end of the structure.