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@@ -1,1033 +1,8 @@ -'\" t -.\" Don't change the line above. it tells man that tbl is needed. -.\" This man page is Copyright (C) 1999 Andi Kleen <ak@muc.de>. -.\" Permission is granted to distribute possibly modified copies -.\" of this page provided the header is included verbatim, -.\" and in case of nontrivial modification author and date -.\" of the modification is added to the header. -.\" $Id: ip.7,v 1.19 2000/12/20 18:10:31 ak Exp $ -.TH IP 7 2001-06-19 "Linux" "Linux Programmer's Manual" -.SH NAME -ip \- Linux IPv4 protocol implementation -.SH SYNOPSIS -.B #include <sys/socket.h> -.br -.\" .B #include <net/netinet.h> -- does not exist anymore -.\" .B #include <linux/errqueue.h> -- never include <linux/foo.h> -.B #include <netinet/in.h> -.br -.B #include <netinet/ip.h> \fR/* superset of previous */ -.sp -.IB tcp_socket " = socket(PF_INET, SOCK_STREAM, 0);" -.br -.IB udp_socket " = socket(PF_INET, SOCK_DGRAM, 0);" -.br -.IB raw_socket " = socket(PF_INET, SOCK_RAW, " protocol ");" -.SH DESCRIPTION -Linux implements the Internet Protocol, version 4, -described in RFC\ 791 and RFC\ 1122. -.B ip -contains a level 2 -multicasting implementation conforming to RFC\ 1112. -It also contains an IP router including a packet filter. -.\" FIXME has someone verified that 2.1 is really 1812 compliant? -.PP -The programming interface is BSD sockets compatible. -For more information on sockets, see -.BR socket (7). -.PP -An IP socket is created by calling the -.BR socket (2) -function as -.BR "socket(PF_INET, socket_type, protocol)" . -Valid socket types are -.B SOCK_STREAM -to open a -.BR tcp (7) -socket, -.B SOCK_DGRAM -to open a -.BR udp (7) -socket, or -.B SOCK_RAW -to open a -.BR raw (7) -socket to access the IP protocol directly. -.I protocol -is the IP protocol in the IP header to be received or sent. -The only valid values for -.I protocol -are -.B 0 -and -.B IPPROTO_TCP -for TCP sockets and -.B 0 -and -.B IPPROTO_UDP -for UDP sockets. -For -.B SOCK_RAW -you may specify -a valid IANA IP protocol defined in -RFC\ 1700 -assigned numbers. -.PP -.\" FIXME ip current does an autobind in listen, but I'm not sure -.\" if that should be documented. -When a process wants to receive new incoming packets or connections, it -should bind a socket to a local interface address using -.BR bind (2). -Only one IP socket may be bound to any given local (address, port) pair. -When -.B INADDR_ANY -is specified in the bind call the socket will be bound to -.I all -local interfaces. -When -.BR listen (2) -or -.BR connect (2) -are called on an unbound socket, it is automatically bound to a -random free port with the local address set to -.BR INADDR_ANY . - -A TCP local socket address that has been bound is unavailable for -some time after closing, -unless the -.B SO_REUSEADDR -flag has been set. -Care should be taken when using this flag as it -makes TCP less reliable. -.SS Address Format -An IP socket address is defined as a combination of an IP interface -address and a 16-bit port number. -The basic IP protocol does not supply port numbers, they -are implemented by higher level protocols like -.BR udp (7) -and -.BR tcp (7). -On raw sockets -.I sin_port -is set to the IP protocol. -.PP -.in +4n -.nf -struct sockaddr_in { - sa_family_t sin_family; /* address family: AF_INET */ - uint16_t sin_port; /* port in network byte order */ - struct in_addr sin_addr; /* internet address */ -}; - -/* Internet address. */ -struct in_addr { - uint32_t s_addr; /* address in network byte order */ -}; -.fi -.in -.PP -.I sin_family -is always set to -.BR AF_INET . -This is required; in Linux 2.2 most networking functions return -.B EINVAL -when this setting is missing. -.I sin_port -contains the port in network byte order. -The port numbers below 1024 are called -.IR "reserved ports" . -Only privileged processes (i.e., those having the -.B CAP_NET_BIND_SERVICE -capability) may -.BR bind (2) -to these sockets. -Note that the raw IPv4 protocol as such has no concept of a -port, they are only implemented by higher protocols like -.BR tcp (7) -and -.BR udp (7). -.PP -.I sin_addr -is the IP host address. -The -.I s_addr -member of -.I struct in_addr -contains the host interface address in network byte order. -.I in_addr -should be assigned one of the INADDR_* values (e.g., -.BR INADDR_ANY ) -or set using the -.BR inet_aton (3), -.BR inet_addr (3), -.BR inet_makeaddr (3) -library functions or directly with the name resolver (see -.BR gethostbyname (3)). -IPv4 addresses are divided into unicast, broadcast -and multicast addresses. -Unicast addresses specify a single interface of a host, -broadcast addresses specify all hosts on a network and multicast -addresses address all hosts in a multicast group. -Datagrams to broadcast addresses can be only sent or received when the -.B SO_BROADCAST -socket flag is set. -In the current implementation connection oriented sockets are only allowed -to use unicast addresses. -.\" Leave a loophole for XTP @) - -Note that the address and the port are always stored in -network byte order. -In particular, this means that you need to call -.BR htons (3) -on the number that is assigned to a port. -All address/port manipulation -functions in the standard library work in network byte order. - -There are several special addresses: -.B INADDR_LOOPBACK -(127.0.0.1) -always refers to the local host via the loopback device; -.B INADDR_ANY -(0.0.0.0) -means any address for binding; -.B INADDR_BROADCAST -(255.255.255.255) -means any host and has the same effect on bind as -.B INADDR_ANY -for historical reasons. -.SS Socket Options -IP supports some protocol-specific socket options that can be set with -.BR setsockopt (2) -and read with -.BR getsockopt (2). -The socket option level for IP is -.BR IPPROTO_IP . -.\" or SOL_IP on Linux -A boolean integer flag is zero when it is false, otherwise true. -.\" -.\" FIXME Document IP_FREEBIND -.\" -.TP -.B IP_OPTIONS -Sets or get the IP options to be sent with every packet from this -socket. -The arguments are a pointer to a memory buffer containing the options -and the option length. -The -.BR setsockopt (2) -call sets the IP options associated with a socket. -The maximum option size for IPv4 is 40 bytes. -See RFC\ 791 for the allowed -options. -When the initial connection request packet for a -.B SOCK_STREAM -socket contains IP options, the IP options will be set automatically -to the options from the initial packet with routing headers reversed. -Incoming packets are not allowed to change options after the connection -is established. -The processing of all incoming source routing options -is disabled by default and can be enabled by using the -.B accept_source_route -sysctl. -Other options like timestamps are still handled. -For datagram sockets, IP options can be only set by the local user. -Calling -.BR getsockopt (2) -with -.B IP_OPTIONS -puts the current IP options used for sending into the supplied buffer. -.TP -.B IP_PKTINFO -Pass an -.B IP_PKTINFO -ancillary message that contains a -.I pktinfo -structure that supplies some information about the incoming packet. -This only works for datagram oriented sockets. -The argument is a flag that tells the socket whether the -.B IP_PKTINFO -message should be passed or not. -The message itself can only be sent/retrieved -as control message with a packet using -.BR recvmsg (2) -or -.BR sendmsg (2). -.IP -.in +4n -.nf -struct in_pktinfo { - unsigned int ipi_ifindex; /* Interface index */ - struct in_addr ipi_spec_dst; /* Local address */ - struct in_addr ipi_addr; /* Header Destination - address */ -}; -.fi -.in -.IP -.\" FIXME elaborate on that. -.I ipi_ifindex -is the unique index of the interface the packet was received on. -.I ipi_spec_dst -is the local address of the packet and -.I ipi_addr -is the destination address in the packet header. -If -.B IP_PKTINFO -is passed to -.BR sendmsg (2) -and -.\" This field is grossly misnamed -.I ipi_spec_dst -is not zero, then it is used as the local source address for the routing -table lookup and for setting up IP source route options. -When -.I ipi_ifindex -is not zero the primary local address of the interface specified by the -index overwrites -.I ipi_spec_dst -for the routing table lookup. -.TP -.B IP_RECVTOS -If enabled the -.B IP_TOS -ancillary message is passed with incoming packets. -It contains a byte which specifies the Type of Service/Precedence -field of the packet header. -Expects a boolean integer flag. -.TP -.B IP_RECVTTL -When this flag is set -pass a -.B IP_TTL -control message with the time to live -field of the received packet as a byte. -Not supported for -.B SOCK_STREAM -sockets. -.TP -.B IP_RECVOPTS -Pass all incoming IP options to the user in a -.B IP_OPTIONS -control message. -The routing header and other options are already filled in -for the local host. -Not supported for -.B SOCK_STREAM -sockets. -.TP -.B IP_RETOPTS -Identical to -.B IP_RECVOPTS -but returns raw unprocessed options with timestamp and route record -options not filled in for this hop. -.TP -.B IP_TOS -Set or receive the Type-Of-Service (TOS) field that is sent -with every IP packet originating from this socket. -It is used to prioritize packets on the network. -TOS is a byte. -There are some standard TOS flags defined: -.B IPTOS_LOWDELAY -to minimize delays for interactive traffic, -.B IPTOS_THROUGHPUT -to optimize throughput, -.B IPTOS_RELIABILITY -to optimize for reliability, -.B IPTOS_MINCOST -should be used for "filler data" where slow transmission doesn't matter. -At most one of these TOS values can be specified. -Other bits are invalid and shall be cleared. -Linux sends -.B IPTOS_LOWDELAY -datagrams first by default, -but the exact behavior depends on the configured queueing discipline. -.\" FIXME elaborate on this -Some high priority levels may require superuser privileges (the -.B CAP_NET_ADMIN -capability). -The priority can also be set in a protocol independent way by the -.RB ( SOL_SOCKET ", " SO_PRIORITY ) -socket option (see -.BR socket (7)). -.TP -.B IP_TTL -Set or retrieve the current time to live field that is used in every packet -sent from this socket. -.TP -.B IP_HDRINCL -If enabled -the user supplies an IP header in front of the user data. -Only valid for -.B SOCK_RAW -sockets. -See -.BR raw (7) -for more information. -When this flag is enabled the values set by -.BR IP_OPTIONS , -.B IP_TTL -and -.B IP_TOS -are ignored. -.TP -.BR IP_RECVERR " (defined in \fI<linux/errqueue.h>\fP)" -Enable extended reliable error message passing. -When enabled on a datagram socket all -generated errors will be queued in a per-socket error queue. -When the user -receives an error from a socket operation the errors can -be received by calling -.BR recvmsg (2) -with the -.B MSG_ERRQUEUE -flag set. -The -.I sock_extended_err -structure describing the error will be passed in an ancillary message with -the type -.B IP_RECVERR -and the level -.BR IPPROTO_IP . -.\" or SOL_IP on Linux -This is useful for reliable error handling on unconnected sockets. -The received data portion of the error queue -contains the error packet. -.IP -The -.B IP_RECVERR -control message contains a -.I sock_extended_err -structure: -.IP -.in +4n -.ne 18 -.nf -#define SO_EE_ORIGIN_NONE 0 -#define SO_EE_ORIGIN_LOCAL 1 -#define SO_EE_ORIGIN_ICMP 2 -#define SO_EE_ORIGIN_ICMP6 3 - -struct sock_extended_err { - uint32_t ee_errno; /* error number */ - uint8_t ee_origin; /* where the error originated */ - uint8_t ee_type; /* type */ - uint8_t ee_code; /* code */ - uint8_t ee_pad; - uint32_t ee_info; /* additional information */ - uint32_t ee_data; /* other data */ - /* More data may follow */ -}; - -struct sockaddr *SO_EE_OFFENDER(struct sock_extended_err *); -.fi -.in -.IP -.I ee_errno -contains the -.I errno -number of the queued error. -.I ee_origin -is the origin code of where the error originated. -The other fields are protocol-specific. -The macro -.B SO_EE_OFFENDER -returns a pointer to the address of the network object -where the error originated from given a pointer to the ancillary message. -If this address is not known, the -.I sa_family -member of the -.I sockaddr -contains -.B AF_UNSPEC -and the other fields of the -.I sockaddr -are undefined. -.IP -IP uses the -.I sock_extended_err -structure as follows: -.I ee_origin -is set to -.B SO_EE_ORIGIN_ICMP -for errors received as an ICMP packet, or -.B SO_EE_ORIGIN_LOCAL -for locally generated errors. -Unknown values should be ignored. -.I ee_type -and -.I ee_code -are set from the type and code fields of the ICMP header. -.I ee_info -contains the discovered MTU for -.B EMSGSIZE -errors. -The message also contains the -.I sockaddr_in of the node -caused the error, which can be accessed with the -.B SO_EE_OFFENDER -macro. -The -.I sin_family -field of the SO_EE_OFFENDER address is -.B AF_UNSPEC -when the source was unknown. -When the error originated from the network, all IP options -.RI ( IP_OPTIONS ", " IP_TTL ", " -etc.) enabled on the socket and contained in the -error packet are passed as control messages. -The payload of the packet -causing the error is returned as normal payload. -.\" FIXME . Is it a good idea to document that? It is a dubious feature. -.\" On -.\" .B SOCK_STREAM -.\" sockets, -.\" .B IP_RECVERR -.\" has slightly different semantics. Instead of -.\" saving the errors for the next timeout, it passes all incoming -.\" errors immediately to the user. -.\" This might be useful for very short-lived TCP connections which -.\" need fast error handling. Use this option with care: -.\" it makes TCP unreliable -.\" by not allowing it to recover properly from routing -.\" shifts and other normal -.\" conditions and breaks the protocol specification. -Note that TCP has no error queue; -.B MSG_ERRQUEUE -is not permitted on -.B SOCK_STREAM -sockets. -.B IP_RECVERR -is valid for TCP, but all errors are -returned by socket function return or -.B SO_ERROR -only. -.IP -For raw sockets, -.B IP_RECVERR -enables passing of all received ICMP errors to the -application, otherwise errors are only reported on connected sockets -.IP -It sets or retrieves an integer boolean flag. -.B IP_RECVERR -defaults to off. -.TP -.B IP_MTU_DISCOVER -Sets or receives the Path MTU Discovery setting -for a socket. -When enabled, Linux will perform Path MTU Discovery -as defined in RFC\ 1191 -on this socket. -The don't fragment flag is set on all outgoing datagrams. -The system-wide default is controlled by the -.B ip_no_pmtu_disc -sysctl for -.B SOCK_STREAM -sockets, and disabled on all others. -For -.RB non- SOCK_STREAM -sockets it is the user's responsibility to packetize the data -in MTU sized chunks and to do the retransmits if necessary. -The kernel will reject packets that are bigger than the known -path MTU if this flag is set (with -.B EMSGSIZE -). -.TS -tab(:); -c l -l l. -Path MTU discovery flags:Meaning -IP_PMTUDISC_WANT:Use per-route settings. -IP_PMTUDISC_DONT:Never do Path MTU Discovery. -IP_PMTUDISC_DO:Always do Path MTU Discovery. -IP_PMTUDISC_PROBE:Set DF but ignore Path MTU. -.TE - -When PMTU discovery is enabled the kernel automatically keeps track of -the path MTU per destination host. -When it is connected to a specific peer with -.BR connect (2) -the currently known path MTU can be retrieved conveniently using the -.B IP_MTU -socket option (e.g., after a -.B EMSGSIZE -error occurred). -It may change over time. -For connectionless sockets with many destinations -the new also MTU for a given destination can also be accessed using the -error queue (see -.BR IP_RECVERR ). -A new error will be queued for every incoming MTU update. - -While MTU discovery is in progress initial packets from datagram sockets -may be dropped. -Applications using UDP should be aware of this and not -take it into account for their packet retransmit strategy. - -To bootstrap the path MTU discovery process on unconnected sockets it -is possible to start with a big datagram size -(up to 64K-headers bytes long) and let it shrink by updates of the -path MTU. -.\" FIXME this is an ugly hack - -To get an initial estimate of the -path MTU connect a datagram socket to the destination address using -.BR connect (2) -and retrieve the MTU by calling -.BR getsockopt (2) -with the -.B IP_MTU -option. - -It is possible to implement RFC 4821 MTU probing with -.B SOCK_DGRAM -or -.B SOCK_RAW -sockets by setting a value of -.BR IP_PMTUDISC_PROBE . -This is also particularly useful for diagnostic tools such as -.BR tracepath (8) -that wish to deliberately send probe packets larger than -the observed Path MTU. -.TP -.B IP_MTU -Retrieve the current known path MTU of the current socket. -Only valid when the socket has been connected. -Returns an integer. -Only valid as a -.BR getsockopt (2). -.\" -.TP -.B IP_ROUTER_ALERT -Pass all to-be forwarded packets with the -IP Router Alert -option -set to this socket. -Only valid for raw sockets. -This is useful, for instance, for user -space RSVP daemons. -The tapped packets are not forwarded by the kernel, it is -the users responsibility to send them out again. -Socket binding is ignored, -such packets are only filtered by protocol. -Expects an integer flag. -.\" -.TP -.B IP_MULTICAST_TTL -Set or reads the time-to-live value of outgoing multicast packets for this -socket. -It is very important for multicast packets to set the smallest TTL possible. -The default is 1 which means that multicast packets don't leave the local -network unless the user program explicitly requests it. -Argument is an -integer. -.\" -.TP -.B IP_MULTICAST_LOOP -Sets or reads a boolean integer argument whether sent multicast -packets should be looped back to the local sockets. -.\" -.TP -.B IP_ADD_MEMBERSHIP -Join a multicast group. -Argument is an -.I ip_mreqn -structure. -.sp -.in +4n -.nf -struct ip_mreqn { - struct in_addr imr_multiaddr; /* IP multicast group - address */ - struct in_addr imr_address; /* IP address of local - interface */ - int imr_ifindex; /* interface index */ -}; -.fi -.in -.sp -.I imr_multiaddr -contains the address of the multicast group the application -wants to join or leave. -It must be a valid multicast address. -.I imr_address -is the address of the local interface with which the system -should join the multicast -group; if it is equal to -.B INADDR_ANY -an appropriate interface is chosen by the system. -.I imr_ifindex -is the interface index of the interface that should join/leave the -.I imr_multiaddr -group, or 0 to indicate any interface. -.IP -For compatibility, the old -.I ip_mreq -structure is still supported. -It differs from -.I ip_mreqn -only by not including -the -.I imr_ifindex -field. -Only valid as a -.BR setsockopt (2). -.\" -.TP -.B IP_DROP_MEMBERSHIP -Leave a multicast group. -Argument is an -.I ip_mreqn -or -.I ip_mreq -structure similar to -.BR IP_ADD_MEMBERSHIP . -.\" -.TP -.B IP_MULTICAST_IF -Set the local device for a multicast socket. -Argument is an -.I ip_mreqn -or -.I ip_mreq -structure similar to -.BR IP_ADD_MEMBERSHIP . -.IP -When an invalid socket option is passed, -.B ENOPROTOOPT -is returned. -.SS Sysctls -The IP protocol -supports the sysctl interface to configure some global options. -The sysctls can be accessed by reading or writing the -.I /proc/sys/net/ipv4/* -files or using the -.\" FIXME As at 2.6.12, 14 Jun 2005, the following are undocumented: -.\" ip_queue_maxlen -.\" ip_conntrack_max -.BR sysctl (2) -interface. -Variables described as -.I Boolean -take an integer value, with a non-zero value ("true") meaning that -the corresponding option is enabled, and a zero value ("false") -meaning that the option is disabled. -.\" -.TP -.BR ip_always_defrag " (Boolean)" -[New with kernel 2.2.13; in earlier kernel versions this feature -was controlled at compile time by the -.B CONFIG_IP_ALWAYS_DEFRAG -option; this option is not present in 2.4.x and later] - -When this boolean frag is enabled (not equal 0) incoming fragments -(parts of IP packets -that arose when some host between origin and destination decided -that the packets were too large and cut them into pieces) will be -reassembled (defragmented) before being processed, even if they are -about to be forwarded. - -Only enable if running either a firewall that is the sole link -to your network or a transparent proxy; never ever use it for a -normal router or host. -Otherwise fragmented communication can be disturbed -if the fragments travel over different links. -Defragmentation also has a large memory and CPU time cost. - -This is automagically turned on when masquerading or transparent -proxying are configured. -.\" -.TP -.B ip_autoconfig -.\" FIXME document ip_autoconfig -Not documented. -.\" -.TP -.BR ip_default_ttl " (integer; default: 64)" -Set the default time-to-live value of outgoing packets. -This can be changed per socket with the -.B IP_TTL -option. -.\" -.TP -.BR ip_dynaddr " (Boolean; default: disabled)" -Enable dynamic socket address and masquerading entry rewriting on interface -address change. -This is useful for dialup interface with changing IP addresses. -0 means no rewriting, 1 turns it on and 2 enables verbose mode. -.\" -.TP -.BR ip_forward " (Boolean; default: disabled)" -Enable IP forwarding with a boolean flag. -IP forwarding can be also set on a per interface basis. -.\" -.TP -.B ip_local_port_range -Contains two integers that define the default local port range -allocated to sockets. -Allocation starts with the first number and ends with the second number. -Note that these should not conflict with the ports used by masquerading -(although the case is handled). -Also arbitrary choices may cause problems with some firewall packet -filters that make assumptions about the local ports in use. -First number should be at least >1024, better >4096 to avoid clashes -with well known ports and to minimize firewall problems. -.\" -.TP -.BR ip_no_pmtu_disc " (Boolean; default: disabled)" -If enabled, don't do Path MTU Discovery for TCP sockets by default. -Path MTU discovery may fail if misconfigured firewalls (that drop -all ICMP packets) or misconfigured interfaces (e.g., a point-to-point -link where the both ends don't agree on the MTU) are on the path. -It is better to fix the broken routers on the path than to turn off -Path MTU Discovery globally, because not doing it incurs a high cost -to the network. -.\" -.\" The following is from 2.6.12: Documentation/networking/ip-sysctl.txt -.TP -.BR ip_nonlocal_bind " (Boolean; default: disabled)" -If set, allows processes to -.BR bind (2) -to non-local IP addresses, -which can be quite useful, but may break some applications. -.\" -.\" The following is from 2.6.12: Documentation/networking/ip-sysctl.txt -.TP -.BR ip6frag_time " (integer; default 30)" -Time in seconds to keep an IPv6 fragment in memory. -.\" -.\" The following is from 2.6.12: Documentation/networking/ip-sysctl.txt -.TP -.BR ip6frag_secret_interval " (integer; default 600)" -Regeneration interval (in seconds) of the hash secret (or lifetime -for the hash secret) for IPv6 fragments. -.TP -.BR ipfrag_high_thresh " (integer), " ipfrag_low_thresh " (integer)" -If the amount of queued IP fragments reaches -.BR ipfrag_high_thresh , -the queue -is pruned down to -.BR ipfrag_low_thresh . -Contains an integer with the number of -bytes. -.TP -.B neigh/* -See -.BR arp (7). -.\" FIXME Document the conf/*/* sysctls -.\" FIXME Document the route/* sysctls -.\" FIXME document them all -.SS Ioctls -All ioctls described in -.BR socket (7) -apply to ip. -.\" 2006-04-02, mtk -.\" commented out the following because ipchains is obsolete -.\" .PP -.\" The ioctls to configure firewalling are documented in -.\" .BR ipfw (4) -.\" from the -.\" .B ipchains -.\" package. -.PP -Ioctls to configure generic device parameters are described in -.BR netdevice (7). -.\" FIXME Add a discussion of multicasting -.SH ERRORS -.\" FIXME document all errors. -.\" We should really fix the kernels to give more uniform -.\" error returns (ENOMEM vs ENOBUFS, EPERM vs EACCES etc.) -.TP -.B EACCES -The user tried to execute an operation without the necessary permissions. -These include: -sending a packet to a broadcast address without having the -.B SO_BROADCAST -flag set; -sending a packet via a -.I prohibit -route; -modifying firewall settings without superuser privileges (the -.B CAP_NET_ADMIN -capability); -binding to a reserved port without superuser privileges (the -.B CAP_NET_BIND_SERVICE -capability). -.TP -.B EADDRINUSE -Tried to bind to an address already in use. -.TP -.B EADDRNOTAVAIL -A nonexistent interface was requested or the requested source -address was -not local. -.TP -.B EAGAIN -Operation on a non-blocking socket would block. -.TP -.B EALREADY -An connection operation on a non-blocking socket is already in progress. -.TP -.B ECONNABORTED -A connection was closed during an -.BR accept (2). -.TP -.B EHOSTUNREACH -No valid routing table entry matches the destination address. -This error can be caused by a ICMP message from a remote router or -for the local routing table. -.TP -.B EINVAL -Invalid argument passed. -For send operations this can be caused by sending to a -.I blackhole -route. -.TP -.B EISCONN -.BR connect (2) -was called on an already connected socket. -.TP -.B EMSGSIZE -Datagram is bigger than an MTU on the path and it cannot be fragmented. -.TP -.BR ENOBUFS ", " ENOMEM -Not enough free memory. -This often means that the memory allocation is limited by the socket -buffer limits, not by the system memory, but this is not -100% consistent. -.TP -.B ENOENT -.B SIOCGSTAMP -was called on a socket where no packet arrived. -.TP -.B ENOPKG -A kernel subsystem was not configured. -.TP -.BR ENOPROTOOPT " and " EOPNOTSUPP -Invalid socket option passed. -.TP -.B ENOTCONN -The operation is only defined on a connected socket, but the socket wasn't -connected. -.TP -.B EPERM -User doesn't have permission to set high priority, change configuration, -or send signals to the requested process or group. -.TP -.B EPIPE -The connection was unexpectedly closed or shut down by the other end. -.TP -.B ESOCKTNOSUPPORT -The socket is not configured or an unknown socket type was requested. -.PP -Other errors may be generated by the overlaying protocols; see -.BR tcp (7), -.BR raw (7), -.BR udp (7) -and -.BR socket (7). -.SH VERSIONS -.BR IP_MTU , -.BR IP_MTU_DISCOVER , -.BR IP_PKTINFO , -.B IP_RECVERR -and -.B IP_ROUTER_ALERT -are new options in Linux 2.2. -They are also all Linux-specific and should not be used in -programs intended to be portable. -.PP -.\" FIXME -.\" To be confirmed that IP_PMTUDISC_PROBE makes it into kernel 2.6.22 -.B IP_PMTUDISC_PROBE -is new in Linux 2.6.22. -.PP -.I struct ip_mreqn -is new in Linux 2.2. -Linux 2.0 only supported -.BR ip_mreq . -.PP -The sysctls were introduced with Linux 2.2. -.SH NOTES -Be very careful with the -.B 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. -.PP -Some other BSD sockets implementations provide -.B IP_RCVDSTADDR -and -.B IP_RECVIF -socket options to get the destination address and the interface of -received datagrams. -Linux has the more general -.B IP_PKTINFO -for the same task. -.PP -Some BSD sockets implementations also provide an -.B IP_RECVTTL -option, but an ancillary message with type -.B IP_RECVTTL -is passed with the incoming packet. -This is different from the -.B IP_TTL -option used in Linux. -.PP -Using -.B SOL_IP -socket options level isn't portable, BSD-based stacks use -.B IPPROTO_IP -level. -.SS Compatibility -For compatibility with Linux 2.0, the obsolete -.BI "socket(PF_INET, SOCK_PACKET, " protocol ) -syntax is still supported to open a -.BR packet (7) -socket. -This is deprecated and should be replaced by -.BI "socket(PF_PACKET, SOCK_RAW, " protocol ) -instead. -The main difference is the new -.I sockaddr_ll -address structure for generic link layer information instead of the old -.BR sockaddr_pkt . -.SH BUGS -There are too many inconsistent error values. -.PP -The ioctls to configure IP-specific interface options and ARP tables are -not described. -.PP -Some versions of glibc forget to declare -.IR in_pktinfo . -Workaround currently is to copy it into your program from this man page. -.PP -Receiving the original destination address with -.B MSG_ERRQUEUE -in -.I msg_name -by -.BR recvmsg (2) -does not work in some 2.2 kernels. -.\" .SH AUTHORS -.\" This man page was written by Andi Kleen. -.SH "SEE ALSO" -.BR recvmsg (2), -.BR sendmsg (2), -.BR byteorder (3), -.BR ipfw (4), -.BR capabilities (7), -.BR netlink (7), -.BR raw (7), -.BR socket (7), -.BR tcp (7), -.BR udp (7) -.PP -RFC\ 791 for the original IP specification. -.br -RFC\ 1122 for the IPv4 host requirements. -.br -RFC\ 1812 for the IPv4 router requirements. -.\" FIXME autobind INADDR REUSEADDR +.TH IP 7 2008-08-07 "Linux" "Linux Programmer's Manual" +.TH IP 7 2008-08-07 "Linux" "Linux Programmer's Manual" +.TH IP 7 2008-08-07 "Linux" "Linux Programmer's Manual" +.TH IP 7 2008-08-07 "Linux" "Linux Programmer's Manual" +.TH IP 7 2008-08-07 "Linux" "Linux Programmer's Manual" +.TH IP 7 2008-08-07 "Linux" "Linux Programmer's Manual" +.TH IP 7 2008-08-07 "Linux" "Linux Programmer's Manual" +.TH IP 7 2008-08-07 "Linux" "Linux Programmer's Manual" |