{
    "mode": "man",
    "parameter": "icmp",
    "section": "7",
    "url": "https://www.chedong.com/phpMan.php/man/icmp/7/json",
    "generated": "2026-10-07T13:54:53Z",
    "sections": {
        "NAME": {
            "content": "icmp - Linux IPv4 ICMP kernel module.\n",
            "subsections": []
        },
        "DESCRIPTION": {
            "content": "This  kernel  protocol  module  implements  the  Internet Control Message Protocol defined in\nRFC 792.  It is used to signal error conditions and for diagnosis.  The user doesn't interact\ndirectly with this module; instead it communicates with the other protocols in the kernel and\nthese pass the ICMP errors to the application layers.  The kernel ICMP  module  also  answers\nICMP requests.\n\nA  user  protocol may receive ICMP packets for all local sockets by opening a raw socket with\nthe protocol IPPROTOICMP.  See raw(7) for more  information.   The  types  of  ICMP  packets\npassed  to  the socket can be filtered using the ICMPFILTER socket option.  ICMP packets are\nalways processed by the kernel too, even when passed to a user socket.\n\nLinux limits the  rate  of  ICMP  error  packets  to  each  destination.   ICMPREDIRECT  and\nICMPDESTUNREACH are also limited by the destination route of the incoming packets.\n",
            "subsections": [
                {
                    "name": "/proc interfaces",
                    "content": "ICMP  supports a set of /proc interfaces to configure some global IP parameters.  The parame‐\nters can be accessed by reading or writing files in the directory /proc/sys/net/ipv4/.   Most\nof  these  parameters  are  rate limitations for specific ICMP types.  Linux 2.2 uses a token\nbucket filter to limit ICMPs.  The value is the timeout in jiffies  until  the  token  bucket\nfilter  is  cleared  after a burst.  A jiffy is a system dependent unit, usually 10ms on i386\nand about 1ms on alpha and ia64.\n\nicmpdestunreachrate (Linux 2.2 to Linux 2.4.9)\nMaximum rate to send ICMP Destination Unreachable packets.  This limits  the  rate  at\nwhich packets are sent to any individual route or destination.  The limit does not af‐\nfect sending of ICMPFRAGNEEDED packets needed for path MTU discovery.\n\nicmpechoignoreall (since Linux 2.2)\nIf this value is nonzero, Linux will ignore all ICMPECHO requests.\n\nicmpechoignorebroadcasts (since Linux 2.2)\nIf  this  value  is nonzero, Linux will ignore all ICMPECHO packets sent to broadcast\naddresses.\n\nicmpechoreplyrate (Linux 2.2 to Linux 2.4.9)\nMaximum rate for sending ICMPECHOREPLY packets in response to ICMPECHOREQUEST  pack‐\nets.\n\nicmperrorsuseinboundifaddr (Boolean; default: disabled; since Linux 2.6.12)\nIf  disabled, ICMP error messages are sent with the primary address of the exiting in‐\nterface.\n\nIf enabled, the message will be sent with the primary address of  the  interface  that\nreceived  the  packet that caused the ICMP error.  This is the behavior that many net‐\nwork administrators will expect from a router.  And it can make debugging  complicated\nnetwork layouts much easier.\n\nNote  that  if  no primary address exists for the interface selected, then the primary\naddress of the first non-loopback interface that has one will be  used  regardless  of\nthis setting.\n\nicmpignoreboguserrorresponses (Boolean; default: disabled; since Linux 2.2)\nSome routers violate RFC1122 by sending bogus responses to broadcast frames.  Such vi‐\nolations  are normally logged via a kernel warning.  If this parameter is enabled, the\nkernel will not give such warnings, which will avoid log file clutter.\n\nicmpparamprobrate (Linux 2.2 to Linux 2.4.9)\nMaximum rate for sending ICMPPARAMETERPROB packets.  These packets are  sent  when  a\npacket arrives with an invalid IP header.\n\nicmpratelimit (integer; default: 1000; since Linux 2.4.10)\nLimit the maximum rates for sending ICMP packets whose type matches icmpratemask (see\nbelow)  to  specific  targets.  0 to disable any limiting, otherwise the minimum space\nbetween responses in milliseconds.\n\nicmpratemask (integer; default: see below; since Linux 2.4.10)\nMask made of ICMP types for which rates are being limited.\n\nSignificant bits: IHGFEDCBA9876543210\nDefault mask:     0000001100000011000 (0x1818)\n\nBit definitions (see the Linux kernel source file include/linux/icmp.h):\n0 Echo Reply\n3 Destination Unreachable *\n4 Source Quench *\n5 Redirect\n8 Echo Request\nB Time Exceeded *\nC Parameter Problem *\nD Timestamp Request\nE Timestamp Reply\nF Info Request\nG Info Reply\nH Address Mask Request\nI Address Mask Reply\n\nThe bits marked with an asterisk are rate limited by default (see the default mask above).\n\nicmptimeexceedrate (Linux 2.2 to Linux 2.4.9)\nMaximum rate for sending ICMPTIMEEXCEEDED packets.  These packets are sent  to  pre‐\nvent loops when a packet has crossed too many hops.\n\npinggrouprange (two integers; default: see below; since Linux 2.6.39)\nRange  of the group IDs (minimum and maximum group IDs, inclusive) that are allowed to\ncreate ICMP Echo sockets.  The default is \"1 0\", which means no group  is  allowed  to\ncreate ICMP Echo sockets.\n"
                }
            ]
        },
        "VERSIONS": {
            "content": "Support for the ICMPADDRESS request was removed in Linux 2.2.\n\nSupport for ICMPSOURCEQUENCH was removed in Linux 2.2.\n",
            "subsections": []
        },
        "NOTES": {
            "content": "As many other implementations don't support IPPROTOICMP raw sockets, this feature should not\nbe relied on in portable programs.\n\nICMPREDIRECT  packets  are not sent when Linux is not acting as a router.  They are also ac‐\ncepted only from the old gateway defined in the routing table and the redirect routes are ex‐\npired after some time.\n\nThe 64-bit  timestamp  returned  by  ICMPTIMESTAMP  is  in  milliseconds  since  the  Epoch,\n1970-01-01 00:00:00 +0000 (UTC).\n\nLinux  ICMP  internally  uses a raw socket to send ICMPs.  This raw socket may appear in net‐\nstat(8) output with a zero inode.\n",
            "subsections": []
        },
        "SEE ALSO": {
            "content": "ip(7), rdisc(8)\n\nRFC 792 for a description of the ICMP protocol.\n\nLinux man-pages 6.7                          2023-10-31                                      icmp(7)",
            "subsections": []
        }
    },
    "summary": "icmp - Linux IPv4 ICMP kernel module.",
    "flags": [],
    "examples": [],
    "see_also": [
        {
            "name": "ip",
            "section": "7",
            "url": "https://www.chedong.com/phpMan.php/man/ip/7/json"
        },
        {
            "name": "rdisc",
            "section": "8",
            "url": "https://www.chedong.com/phpMan.php/man/rdisc/8/json"
        }
    ]
}