Home
Main website
Display Sidebar
Hide Ads
Recent Changes
View Source:
icmp(7)
Edit
PageHistory
Diff
Info
LikePages
ICMP !!!ICMP NAME DESCRIPTION SYSCTLS NOTES VERSIONS SEE ALSO ---- !!NAME icmp, IPPROTO_ICMP - Linux IPv4 ICMP kernel module. !!DESCRIPTION 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 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(7) 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 limits the rate of ICMP error packets to each destination. __ICMP_REDIRECT__ and __ICMP_DEST_UNREACH__ are also limited by the destination route of the incoming packets. !!SYSCTLS 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 jiffies until the token bucket filter is cleared after a burst. A jiffy is a system dependent unit, usually 10ms on x86 and about 1ms on alpha and IA64. __icmp_destunreach_rate__ Maximum rate to send ICMP Destination Unreachable packets. This limits the rate at which packets are sent to any individual route or destination. The limit does not affect sending of __ICMP_FRAG_NEEDED__ packets needed for path MTU discovery. __icmp_echo_ignore_all__ If this value is non-zero, Linux will ignore all __ICMP_ECHO__ requests. __icmp_echo_ignore_broadcasts__ If this value is non-zero, Linux will ignore all __ICMP_ECHO__ packets sent to broadcast addresses. __icmp_echoreply_rate__ Maximum rate for sending __ICMP_ECHOREPLY__ packets in response to __ICMP_ECHOREQUEST__ packets. __icmp_paramprob_rate__ Maximum rate for sending __ICMP_PARAMETERPROB__ packets. These packets are sent when a packet arrives with an invalid IP header. __icmp_timeexceed_rate__ Maximum rate for sending __ICMP_TIME_EXCEEDED__ packets. These packets are sent to prevent loops when a packet has crossed too many hops. !!NOTES As many other implementations 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. !!VERSIONS Support for the __ICMP_ADDRESS__ request was removed in 2.2. Support for __ICMP_SOURCE_QUENCH__ was removed in Linux 2.2. !!SEE ALSO ip(7) RFC792 for a description of the ICMP protocol. ----
One page links to
icmp(7)
:
Man7i
This page is a man page (or other imported legacy content). We are unable to automatically determine the license status of this page.
