tree-wide: remove Emacs lines from all files This should be handled fine now by .dir-locals.el, so need to carry that stuff in every file.

dhcp: make DHCP_OPTION_* enum public libsystemd-network provides the public function sd_dhcp_client_set_request_option() to enable the request of a given DHCP option. However the enum defining such options is defined in the internal header dhcp-protocol.h. Move the enum definition to the public header sd-dhcp-client.h and properly namespace values.

sd-dhcp: parse error message in DECLINE or NAK If a client sends a DECLINE or a server sends a NAK, they can include a string with a message to explain the error. Parse this and print it at debug level.

tree-wide: sort includes Sort the includes accoding to the new coding style.

network: s/user_data/userdata/ Everywhere else we call the generic user data pointer just "userdata", rather than "user_data". Let's do this here, too.

sd-dhcp: option_append - support falling back to 'sname' and 'file'

sd-dhcp: make sure we can not fill options so much that there is no space for END

sd-dhcp: refactor parse_options Similar to the previous patch, exchange a length and a pointer with only one offset variable. Also fix the type of the options to be uint8_t[], rather than uint8_t*.

sd-dhcp: refactor dhcp_option_append Store a pointer to the options in the DHCPMessage struct, and pass this together with an offset around, rather than a uint8_t**. This avoids us having to (re)compute the pointer; and changes dhcp_option_append from adjusting both the pointer to the next option and the remaining size of the options, to just adjusting the current offset. This makes the code a bit simpler to follow IMHO, but there should be no functional change.

sd-dhcp-client: move magic cookie into DHCPMessage struct Also move the checking of it to the main message handler, rather than the options parser. Fix a bug, so we now drop the packet if any of the magic bytes don't match. Before we used to only drop the packet if they were all wrong.

sd-network: add new library This is similar to sd-login, but exposes the state of networkd rather than logind. Include it in libsystemd-dhcp and rename it to libsystemd-network.