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.

util-lib: split out fd-related operations into fd-util.[ch] There are more than enough to deserve their own .c file, hence move them over.

lldp: move lldp_receive_packet() to lldp-internal.c In order to implement tests for the LLDP state machine, we need to mock lldp_network_bind_raw_socket(). Move the other function lldp_receive_packet() to another file so that we can replace the first function with a custom one and keep the second one.

lldp: export opaque TLV type and accessor functions Export struct tlv_packet as a public opaque sd_lldp_packet type and make its accessor functions public.

remove unused includes This patch removes includes that are not used. The removals were found with include-what-you-use which checks if any of the symbols from a header is in use.

sd-lldp: minor header cleanup * (potentially) public headers must reside in src/systemd/ (not in src/libsystemd*) * some private (not prefixed with sd_) functions moved from sd-lldp.h to lldp-internal.h * introduce lldp-util.h for the cleanup macro, as these should not be public * rename the cleanup macro, we always name them _cleanup_foo_, never _cleanup_sd_foo_ * mark some function arguments as 'const'

networkd: Introduce Link Layer Discovery Protocol (LLDP) This patch introduces LLDP support to networkd. it implements the receiver side of the protocol. The Link Layer Discovery Protocol (LLDP) is an industry-standard, vendor-neutral method to allow networked devices to advertise capabilities, identity, and other information onto a LAN. The Layer 2 protocol, detailed in IEEE 802.1AB-2005.LLDP allows network devices that operate at the lower layers of a protocol stack (such as Layer 2 bridges and switches) to learn some of the capabilities and characteristics of LAN devices available to higher layer protocols.