bsd/man/man4/icmp6.4

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  31 .Dd December 20, 2004
  32 .Dt ICMP6 4
  33 .Os
  34 .Sh NAME
  35 .Nm icmp6
  36 .Nd Internet Control Message Protocol for IPv6
  37 .Sh SYNOPSIS
  38 .In sys/socket.h
  39 .In netinet/in.h
  40 .In netinet/icmp6.h
  41 .Ft int
  42 .Fn socket AF_INET6 SOCK_RAW IPPROTO_ICMPV6
  43 .Sh DESCRIPTION
  44 ICMPv6 is the error and control message protocol used by IPv6 and the
  45 IPv6 protocol family (see
  46 .Xr ip6 4
  47 and
  48 .Xr inet6 4 ) .
  49 It may be accessed through a
  50 .Dq raw socket
  51 for network monitoring and diagnostic functions.
  52 .Pp
  53 The
  54 .Fa proto
  55 parameter to the
  56 .Xr socket 2
  57 call to create an ICMPv6 socket may be obtained from
  58 .Xr getprotobyname 3 .
  59 ICMPv6 sockets are connectionless, and are normally used with the
  60 .Xr sendto 2
  61 and
  62 .Xr recvfrom 2
  63 calls, though the
  64 .Xr connect 2
  65 call may also be used to fix the destination for future packets
  66 (in which case
  67 .Xr read 2
  68 or
  69 .Xr recv 2
  70 and
  71 .Xr write 2
  72 or
  73 .Xr send 2
  74 system calls may be used).
  75 .Pp
  76 Outgoing packets automatically have an IPv6 header prepended to them
  77 (based on the destination address).
  78 Incoming packets on the socket are received with the IPv6 header and any
  79 extension headers removed.
  80 .Ss Types
  81 ICMPv6 messages are classified according to the type and code fields
  82 present in the ICMPv6 header.
  83 The abbreviations for the types and codes may be used in rules in
  84 .Xr pf.conf 5 .
  85 The following types are defined:
  86 .Bl -column x xxxxxxxxxxxx -offset indent
  87 .It Sy Num Ta Sy Abbrev. Ta Sy Description
  88 .It 1 Ta unreach Ta "Destination unreachable"
  89 .It 2 Ta toobig Ta "Packet too big"
  90 .It 3 Ta timex Ta "Time exceeded"
  91 .It 4 Ta paramprob Ta "Invalid IPv6 header"
  92 .It 128 Ta echoreq Ta "Echo service request"
  93 .It 129 Ta echorep Ta "Echo service reply"
  94 .It 130 Ta groupqry Ta "Group membership query"
  95 .It 130 Ta listqry Ta "Multicast listener query"
  96 .It 131 Ta grouprep Ta "Group membership report"
  97 .It 131 Ta listenrep Ta "Multicast listener report"
  98 .It 132 Ta groupterm Ta "Group membership termination"
  99 .It 132 Ta listendone Ta "Multicast listerner done"
 100 .It 133 Ta routersol Ta "Router solicitation"
 101 .It 134 Ta routeradv Ta "Router advertisement"
 102 .It 135 Ta neighbrsol Ta "Neighbor solicitation"
 103 .It 136 Ta neighbradv Ta "Neighbor advertisement"
 104 .It 137 Ta redir Ta "Shorter route exists"
 105 .It 138 Ta routrrenum Ta "Route renumbering"
 106 .It 139 Ta fqdnreq Ta "FQDN query"
 107 .It 139 Ta niqry Ta "Node information query"
 108 .It 139 Ta wrureq Ta "Who-are-you request"
 109 .It 140 Ta fqdnrep Ta "FQDN reply"
 110 .It 140 Ta nirep Ta "Node information reply"
 111 .It 140 Ta wrurep Ta "Who-are-you reply"
 112 .It 200 Ta mtraceresp Ta "mtrace response"
 113 .It 201 Ta mtrace Ta "mtrace messages"
 114 .El
 115 .Pp
 116 The following codes are defined:
 117 .Bl -column x xxxxxxxxxxxx xxxxxxxx -offset indent
 118 .It Sy Num Ta Sy Abbrev. Ta Sy Type Ta
 119 .Sy Description
 120 .It 0 Ta noroute-unr Ta unreach Ta "No route to destination"
 121 .It 1 Ta admin-unr Ta unreach Ta "Administratively prohibited"
 122 .It 2 Ta beyond-unr Ta unreach Ta "Beyond scope of source address"
 123 .It 2 Ta notnbr-unr Ta unreach Ta "Not a neighbor (obselete)"
 124 .It 3 Ta addr-unr Ta unreach Ta "Address unreachable"
 125 .It 4 Ta port-unr Ta unreach Ta "Port unreachable"
 126 .It 0 Ta transit Ta timex Ta "Time exceeded in transit"
 127 .It 1 Ta reassemb Ta timex Ta "Time exceeded in reassembly"
 128 .It 0 Ta badhead Ta paramprob Ta "Erroneous header field"
 129 .It 1 Ta nxthdr Ta paramprob Ta "Unrecognized next header"
 130 .It 2 Ta "" Ta redir Ta "Unrecognized option"
 131 .It 0 Ta redironlink Ta redir Ta "Redirection to on-link node"
 132 .It 1 Ta redirrouter Ta redir Ta "Redirection to better router"
 133 .El
 134 .Ss Headers
 135 All ICMPv6 messages are prefixed with an ICMPv6 header.
 136 This header corresponds to the
 137 .Vt icmp6_hdr
 138 structure and has the following definition:
 139 .Bd -literal -offset indent
 140 struct icmp6_hdr {
 141         u_int8_t        icmp6_type;     /* type field */
 142         u_int8_t        icmp6_code;     /* code field */
 143         u_int16_t       icmp6_cksum;    /* checksum field */
 144         union {
 145                 u_int32_t icmp6_un_data32[1]; /* type-specific */
 146                 u_int16_t icmp6_un_data16[2]; /* type-specific */
 147                 u_int8_t  icmp6_un_data8[4];  /* type-specific */
 148         } icmp6_dataun;
 149 } __packed;
 150
 151 #define icmp6_data32    icmp6_dataun.icmp6_un_data32
 152 #define icmp6_data16    icmp6_dataun.icmp6_un_data16
 153 #define icmp6_data8     icmp6_dataun.icmp6_un_data8
 154 #define icmp6_pptr      icmp6_data32[0] /* parameter prob */
 155 #define icmp6_mtu       icmp6_data32[0] /* packet too big */
 156 #define icmp6_id        icmp6_data16[0] /* echo request/reply */
 157 #define icmp6_seq       icmp6_data16[1] /* echo request/reply */
 158 #define icmp6_maxdelay  icmp6_data16[0] /* mcast group membership*/
 159 .Ed
 160 .Pp
 161 .Va icmp6_type
 162 describes the type of the message.
 163 Suitable values are defined in
 164 .Aq Pa netinet/icmp6.h .
 165 .Va icmp6_code
 166 describes the sub-type of the message and depends on
 167 .Va icmp6_type .
 168 .Va icmp6_cksum
 169 contains the checksum for the message and is filled in by the
 170 kernel on outgoing messages.
 171 The other fields are used for type-specific purposes.
 172 .Ss Filters
 173 Because of the extra functionality of ICMPv6 in comparison to ICMPv4,
 174 a larger number of messages may be potentially received on an ICMPv6
 175 socket.
 176 Input filters may therefore be used to restrict input to a subset of the
 177 incoming ICMPv6 messages so only interesting messages are returned by the
 178 .Xr recv 2
 179 family of calls to an application.
 180 .Pp
 181 The
 182 .Vt icmp6_filter
 183 structure may be used to refine the input message set according to the
 184 ICMPv6 type.
 185 By default, all messages types are allowed on newly created raw ICMPv6
 186 sockets.
 187 The following macros may be used to refine the input set:
 188 .Bl -tag -width Ds
 189 .It Fn "void ICMP6_FILTER_SETPASSALL" "struct icmp6_filter *filterp"
 190 Allow all incoming messages.
 191 .Va filterp
 192 is modified to allow all message types.
 193 .It Fn "void ICMP6_FILTER_SETBLOCKALL" "struct icmp6_filter *filterp"
 194 Ignore all incoming messages.
 195 .Va filterp
 196 is modified to ignore all message types.
 197 .It Fn "void ICMP6_FILTER_SETPASS" "int type" \
 198     "struct icmp6_filter *filterp"
 199 Allow ICMPv6 messages with the given
 200 .Fa type .
 201 .Va filterp
 202 is modified to allow such messages.
 203 .It Fn "void ICMP6_FILTER_SETBLOCK" "int type" \
 204     "struct icmp6_filter *filterp"
 205 Ignore ICMPv6 messages with the given
 206 .Fa type .
 207 .Va filterp
 208 is modified to ignore such messages.
 209 .It Fn "int ICMP6_FILTER_WILLPASS" "int type" \
 210     "const struct icmp6_filter *filterp"
 211 Determine if the given filter will allow an ICMPv6 message of the given
 212 type.
 213 .It Fn "int ICMP6_FILTER_WILLBLOCK" "int type" \
 214     "const struct icmp6_filter *filterp"
 215 Determine if the given filter will ignore an ICMPv6 message of the given
 216 type.
 217 .El
 218 .Pp
 219 The
 220 .Xr getsockopt 2
 221 and
 222 .Xr setsockopt 2
 223 calls may be used to obtain and install the filter on ICMPv6 sockets at
 224 option level
 225 .Dv IPPROTO_ICMPV6
 226 and name
 227 .Dv ICMPV6_FILTER
 228 with a pointer to the
 229 .Vt icmp6_filter
 230 structure as the option value.
 231 .Ss "Non-privileged ICMPv6"
 232 .Pp
 233 .Tn ICMPv6
 234 sockets can be opened with the
 235 .Dv SOCK_DGRAM
 236 socket type without requiring root privileges. The synopsis is the following:
 237 .Pp
 238 .Fn socket AF_INET6 SOCK_DGRAM IPPROTO_ICMP6
 239 .Pp
 240 This can only be used to send
 241 .Tn ICMPv6
 242 echo requests to gauge the quality of the connectivity to a host, to receive
 243 destination unreachable message for path MTU discovery, or to receveive
 244 time exceeded message for traceroute.
 245 .Pp
 246 A socket opened with superuser privileges can send any kind of
 247 .Tn ICMPv6
 248 message and can also use the
 249 .Xr ip6 4
 250 options that require superuser privileges.
 251 .Sh SEE ALSO
 252 .Xr getsockopt 2 ,
 253 .Xr recv 2 ,
 254 .Xr send 2 ,
 255 .Xr setsockopt 2 ,
 256 .Xr socket 2 ,
 257 .Xr getprotobyname 3 ,
 258 .Xr inet6 4 ,
 259 .Xr ip6 4 ,
 260 .Xr netintro 4
 261 .Rs
 262 .%A W. Stevens
 263 .%A M. Thomas
 264 .%T Advanced Sockets API for IPv6
 265 .%N RFC 2292
 266 .%D February 1998
 267 .Re
 268 .Rs
 269 .%A A. Conta
 270 .%A S. Deering
 271 .%T "Internet Control Message Protocol (ICMPv6) for the Internet" \
 272     "Protocol Version 6 (IPv6) Specification"
 273 .%N RFC 2463
 274 .%D December 1998
 275 .Re