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icmp (4)
  • icmp (4) ( FreeBSD man: Специальные файлы /dev/* )
  • >> icmp (4) ( Linux man: Специальные файлы /dev/* )
  • icmp (7) ( Solaris man: Макропакеты и соглашения )
  • icmp (7) ( Русские man: Макропакеты и соглашения )
  • icmp (7) ( Linux man: Макропакеты и соглашения )
  • Ключ icmp обнаружен в базе ключевых слов.


    icmp, IPPROTO_ICMP - Linux IPv4 ICMP kernel module. 


    This kernel protocol module implements the Internet Control Message Protocol defined in RFC792. It is used to signal error conditions and for diagnosis. The user doesn't interact directly with this module; instead it communicates with the other protocols in the kernel and these pass the ICMP errors to the application layers. The kernel ICMP module also answers to ICMP requests.

    A user protocol may receive ICMP packets for all local sockets by opening a RAW socket with the protocol IPPROTO_ICMP. See raw(4) for more information. The types of ICMP packets passed to the socket can be filtered using the ICMP_FILTER socket option. ICMP packets are always processed by the kernel too, even when passed to a user socket.

    Linux rate limits ICMP error packets per destination. ICMP_REDIRECT and ICMP_DEST_UNREACH are limited per destination route of the incoming packets.



    ICMP supports a sysctl interface to configure some global IP parameters. The sysctls can be accessed by reading or writing the /proc/sys/net/ipv4/* files or with the sysctl(2) interface. Most of these sysctls are rate limitations for specific ICMP types. Linux 2.2 uses a token bucket filter to limit ICMPs. The value is the timeout in seconds until the token bucket filter is cleared.
    Maximum rate to send ICMP Destination Unreachable packets. They are are limited per route and additionally per destination. This sysctl limits the per destination rate and are local per destination. The limit does not affect sending of ICMP_FRAG_NEEDED packets needed for path mtu discovery.
    Ignore all ICMP_ECHO requests if not zero.
    Ignore ICMP_ECHO packets sent to broadcast addresses if not zero.
    Maximum rate for outgoing ICMP_ECHOREPLY packets sent in response to ICMP_ECHOREQUEST packets.
    Maximum rate for outgoing ICMP_PARAMETERPROB packets sent. These packets are sent when a packet arrives with an invalid IP header.
    Maximum rate for outgoing ICMP_TIME_EXCEEDED packets sent. These packets are sent to prevent loops when a packet has crossed too many hops.


    As many other OSes don't support IPPROTO_ICMP raw sockets, this feature should not be relied on in portable programs.

    ICMP_REDIRECT packets are not sent when Linux is not acting as a router. They are also only accepted from the old gateway defined in the routing table and the redirect routes are expired after some time.

    The 64-bit timestamp returned by ICMP_TIMESTAMP is in milliseconds since January 1, 1970.

    Linux ICMP internally uses a raw socket to send ICMPs. This raw socket may appear in netstat(8) output with a zero inode.



    Support for the ICMP_ADDRESS_MASK request was removed in 2.2.

    Support for ICMP_SOURCE_QUENCH was removed in Linux 2.2.  



    RFC792 for a description of the ICMP protocol.




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