реализация протокола IPv4 в Linux (Linux IPv4 protocol implementation)
Примечание (Note)
IP_FREEBIND, IP_MSFILTER, IP_MTU, IP_MTU_DISCOVER,
IP_RECVORIGDSTADDR, IP_PASSSEC, IP_PKTINFO, IP_RECVERR,
IP_ROUTER_ALERT, and IP_TRANSPARENT are Linux-specific.
Be very careful with the SO_BROADCAST option - it is not
privileged in Linux. It is easy to overload the network with
careless broadcasts. For new application protocols it is better
to use a multicast group instead of broadcasting. Broadcasting
is discouraged.
Some other BSD sockets implementations provide IP_RCVDSTADDR and
IP_RECVIF socket options to get the destination address and the
interface of received datagrams. Linux has the more general
IP_PKTINFO for the same task.
Some BSD sockets implementations also provide an IP_RECVTTL
option, but an ancillary message with type IP_RECVTTL is passed
with the incoming packet. This is different from the IP_TTL
option used in Linux.
Using the SOL_IP socket options level isn't portable; BSD-based
stacks use the IPPROTO_IP level.
INADDR_ANY (0.0.0.0) and INADDR_BROADCAST (255.255.255.255) are
byte-order-neutral.
This means htonl(3) has no effect on them.
Compatibility
For compatibility with Linux 2.0, the obsolete socket(AF_INET,
SOCK_PACKET, protocol) syntax is still supported to open a
packet(7) socket. This is deprecated and should be replaced by
socket(AF_PACKET, SOCK_RAW, protocol) instead. The main
difference is the new sockaddr_ll address structure for generic
link layer information instead of the old sockaddr_pkt.
