kernel/network: Fix ICMPv6 checksum calculation

Ensure that any overflow bits aren't lost when returning from the
helper function. These need to added to the least significant bits in
ipv6_checksum.

Change-Id: Ida9821dd87d34ac1982703d9861419ed97ab4b9e
Reviewed-on: https://review.haiku-os.org/c/haiku/+/6036
Reviewed-by: waddlesplash <waddlesplash@gmail.com>
Reviewed-by: Adrien Destugues <pulkomandy@pulkomandy.tk>
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>

Work in progress commit by Atis Elsts (I'm posting his ChangeLog comments
directly here), I made only a few style changes:
* introduced 'has_broadcast_address' field in
struct net_address_module_info
- REVIEW: the name, and the status of this field for UNIX and L2CAP
families
* ipv6 address family support
* ipv6 address printing
* ipv6 protocol support
* ipv6 multicast support
- TODO: add and remove multicast routes in a more proper way
- TODO: support MLD
* ipv6 datalink protocol support
* icmpv6 protocol support (EchoRequest and EchoResponse messages)
* ipv6 neigbor discovery protocol support
(Advertisement and Solicitation messages)
- TODO: only the very basic support is present,
the protocol state machine is by no means completed
- TODO: replying to Solicitation does not work too good ATM
(visible, when pinging Haiku from outside)
* added Jenkin's hash algorith
* minor changes in existing IPv4 code - cleanup function
ipv4_get_loopback_address(), written by myself
* add tests: raw, udp, tcp/udp, mullicast sender
* add 'hoplimit' field in struct net_buffer
- TODO: this is just a hack, more generic approach would be better.
* add 'receive_data' function pointer in
struct net_datalink_protocol_module_info
- TODO: this is also more like a hack, to support information
passing from ICMPv6 to IPv6_datagram level.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@37604 a95241bf-73f2-0310-859d-f6bbb57e9c96

Work in progress commit by Atis Elsts (I'm posting his ChangeLog comments
directly here), I made only a few style changes:
* introduced 'has_broadcast_address' field in
struct net_address_module_info
- REVIEW: the name, and the status of this field for UNIX and L2CAP
families
* ipv6 address family support
* ipv6 address printing
* ipv6 protocol support
* ipv6 multicast support
- TODO: add and remove multicast routes in a more proper way
- TODO: support MLD
* ipv6 datalink protocol support
* icmpv6 protocol support (EchoRequest and EchoResponse messages)
* ipv6 neigbor discovery protocol support
(Advertisement and Solicitation messages)
- TODO: only the very basic support is present,
the protocol state machine is by no means completed
- TODO: replying to Solicitation does not work too good ATM
(visible, when pinging Haiku from outside)
* added Jenkin's hash algorith
* minor changes in existing IPv4 code - cleanup function
ipv4_get_loopback_address(), written by myself
* add tests: raw, udp, tcp/udp, mullicast sender
* add 'hoplimit' field in struct net_buffer
- TODO: this is just a hack, more generic approach would be better.
* add 'receive_data' function pointer in
struct net_datalink_protocol_module_info
- TODO: this is also more like a hack, to support information
passing from ICMPv6 to IPv6_datagram level.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@37604 a95241bf-73f2-0310-859d-f6bbb57e9c96