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diff --git a/man7/netlink.7 b/man7/netlink.7 deleted file mode 100644 index e0e14f4..0000000 --- a/man7/netlink.7 +++ /dev/null @@ -1,611 +0,0 @@ -'\" t -.\" This man page is Copyright (c) 1998 by Andi Kleen. -.\" -.\" SPDX-License-Identifier: GPL-1.0-or-later -.\" -.\" Based on the original comments from Alexey Kuznetsov -.\" Modified 2005-12-27 by Hasso Tepper <hasso@estpak.ee> -.\" $Id: netlink.7,v 1.8 2000/06/22 13:23:00 ak Exp $ -.TH netlink 7 2023-10-31 "Linux man-pages 6.7" -.SH NAME -netlink \- communication between kernel and user space (AF_NETLINK) -.SH SYNOPSIS -.nf -.B #include <asm/types.h> -.B #include <sys/socket.h> -.B #include <linux/netlink.h> -.P -.BI "netlink_socket = socket(AF_NETLINK, " socket_type ", " netlink_family ); -.fi -.SH DESCRIPTION -Netlink is used to transfer information between the kernel and -user-space processes. -It consists of a standard sockets-based interface for user space -processes and an internal kernel API for kernel modules. -The internal kernel interface is not documented in this manual page. -There is also an obsolete netlink interface -via netlink character devices; this interface is not documented here -and is provided only for backward compatibility. -.P -Netlink is a datagram-oriented service. -Both -.B SOCK_RAW -and -.B SOCK_DGRAM -are valid values for -.IR socket_type . -However, the netlink protocol does not distinguish between datagram -and raw sockets. -.P -.I netlink_family -selects the kernel module or netlink group to communicate with. -The currently assigned netlink families are: -.TP -.B NETLINK_ROUTE -Receives routing and link updates and may be used to modify the routing -tables (both IPv4 and IPv6), IP addresses, link parameters, -neighbor setups, queueing disciplines, traffic classes, and -packet classifiers (see -.BR rtnetlink (7)). -.TP -.BR NETLINK_W1 " (Linux 2.6.13 to Linux 2.16.17)" -Messages from 1-wire subsystem. -.TP -.B NETLINK_USERSOCK -Reserved for user-mode socket protocols. -.TP -.BR NETLINK_FIREWALL " (up to and including Linux 3.4)" -.\" removed by commit d16cf20e2f2f13411eece7f7fb72c17d141c4a84 -Transport IPv4 packets from netfilter to user space. -Used by -.I ip_queue -kernel module. -After a long period of being declared obsolete (in favor of the more advanced -.I nfnetlink_queue -feature), -.B NETLINK_FIREWALL -was removed in Linux 3.5. -.TP -.BR NETLINK_SOCK_DIAG " (since Linux 3.3)" -.\" commit 7f1fb60c4fc9fb29fbb406ac8c4cfb4e59e168d6 -Query information about sockets of various protocol families from the kernel -(see -.BR sock_diag (7)). -.TP -.BR NETLINK_INET_DIAG " (since Linux 2.6.14)" -An obsolete synonym for -.BR NETLINK_SOCK_DIAG . -.TP -.BR NETLINK_NFLOG " (up to and including Linux 3.16)" -Netfilter/iptables ULOG. -.TP -.B NETLINK_XFRM -.\" FIXME More details on NETLINK_XFRM needed. -IPsec. -.TP -.BR NETLINK_SELINUX " (since Linux 2.6.4)" -SELinux event notifications. -.TP -.BR NETLINK_ISCSI " (since Linux 2.6.15)" -.\" FIXME More details on NETLINK_ISCSI needed. -Open-iSCSI. -.TP -.BR NETLINK_AUDIT " (since Linux 2.6.6)" -.\" FIXME More details on NETLINK_AUDIT needed. -Auditing. -.TP -.BR NETLINK_FIB_LOOKUP " (since Linux 2.6.13)" -.\" FIXME More details on NETLINK_FIB_LOOKUP needed. -Access to FIB lookup from user space. -.TP -.BR NETLINK_CONNECTOR " (since Linux 2.6.14)" -Kernel connector. -See -.I Documentation/driver\-api/connector.rst -(or -.I /Documentation/connector/connector.* -.\" commit baa293e9544bea71361950d071579f0e4d5713ed -in Linux 5.2 and earlier) -in the Linux kernel source tree for further information. -.TP -.BR NETLINK_NETFILTER " (since Linux 2.6.14)" -.\" FIXME More details on NETLINK_NETFILTER needed. -Netfilter subsystem. -.TP -.BR NETLINK_SCSITRANSPORT " (since Linux 2.6.19)" -.\" commit 84314fd4740ad73550c76dee4a9578979d84af48 -.\" FIXME More details on NETLINK_SCSITRANSPORT needed. -SCSI Transports. -.TP -.BR NETLINK_RDMA " (since Linux 3.0)" -.\" commit b2cbae2c248776d81cc265ff7d48405b6a4cc463 -.\" FIXME More details on NETLINK_RDMA needed. -Infiniband RDMA. -.TP -.BR NETLINK_IP6_FW " (up to and including Linux 3.4)" -Transport IPv6 packets from netfilter to user space. -Used by -.I ip6_queue -kernel module. -.TP -.B NETLINK_DNRTMSG -DECnet routing messages. -.TP -.BR NETLINK_KOBJECT_UEVENT " (since Linux 2.6.10)" -.\" FIXME More details on NETLINK_KOBJECT_UEVENT needed. -Kernel messages to user space. -.TP -.BR NETLINK_GENERIC " (since Linux 2.6.15)" -Generic netlink family for simplified netlink usage. -.TP -.BR NETLINK_CRYPTO " (since Linux 3.2)" -.\" commit a38f7907b926e4c6c7d389ad96cc38cec2e5a9e9 -.\" Author: Steffen Klassert <steffen.klassert@secunet.com> -Netlink interface to request information about ciphers registered -with the kernel crypto API as well as allow configuration of the -kernel crypto API. -.P -Netlink messages consist of a byte stream with one or multiple -.I nlmsghdr -headers and associated payload. -The byte stream should be accessed only with the standard -.B NLMSG_* -macros. -See -.BR netlink (3) -for further information. -.P -In multipart messages (multiple -.I nlmsghdr -headers with associated payload in one byte stream) the first and all -following headers have the -.B NLM_F_MULTI -flag set, except for the last header which has the type -.BR NLMSG_DONE . -.P -After each -.I nlmsghdr -the payload follows. -.P -.in +4n -.EX -struct nlmsghdr { - __u32 nlmsg_len; /* Length of message including header */ - __u16 nlmsg_type; /* Type of message content */ - __u16 nlmsg_flags; /* Additional flags */ - __u32 nlmsg_seq; /* Sequence number */ - __u32 nlmsg_pid; /* Sender port ID */ -}; -.EE -.in -.P -.I nlmsg_type -can be one of the standard message types: -.B NLMSG_NOOP -message is to be ignored, -.B NLMSG_ERROR -message signals an error and the payload contains an -.I nlmsgerr -structure, -.B NLMSG_DONE -message terminates a multipart message. -Error messages get the -original request appended, unless the user requests to cap the -error message, and get extra error data if requested. -.P -.in +4n -.EX -struct nlmsgerr { - int error; /* Negative errno or 0 for acknowledgements */ - struct nlmsghdr msg; /* Message header that caused the error */ - /* - * followed by the message contents - * unless NETLINK_CAP_ACK was set - * or the ACK indicates success (error == 0). - * For example Generic Netlink message with attributes. - * message length is aligned with NLMSG_ALIGN() - */ - /* - * followed by TLVs defined in enum nlmsgerr_attrs - * if NETLINK_EXT_ACK was set - */ -}; -.EE -.in -.P -A netlink family usually specifies more message types, see the -appropriate manual pages for that, for example, -.BR rtnetlink (7) -for -.BR NETLINK_ROUTE . -.TS -tab(:); -l s -lB lx. -Standard flag bits in \fInlmsg_flags\fP -_ -NLM_F_REQUEST:T{ -Must be set on all request messages. -T} -NLM_F_MULTI:T{ -The message is part of a multipart message terminated by -.BR NLMSG_DONE . -T} -NLM_F_ACK:T{ -Request for an acknowledgement on success. -T} -NLM_F_ECHO:T{ -Echo this request. -T} -.TE -.\" No right adjustment for text blocks in tables -.TS -tab(:); -l s -lB lx. -Additional flag bits for GET requests -_ -NLM_F_ROOT:T{ -Return the complete table instead of a single entry. -T} -NLM_F_MATCH:T{ -Return all entries matching criteria passed in message content. -Not implemented yet. -T} -NLM_F_ATOMIC:T{ -Return an atomic snapshot of the table. -T} -NLM_F_DUMP:T{ -Convenience macro; equivalent to -(NLM_F_ROOT|NLM_F_MATCH). -T} -.TE -.\" FIXME NLM_F_ATOMIC is not used anymore? -.P -Note that -.B NLM_F_ATOMIC -requires the -.B CAP_NET_ADMIN -capability or an effective UID of 0. -.TS -tab(:); -l s -lB lx. -Additional flag bits for NEW requests -_ -NLM_F_REPLACE:T{ -Replace existing matching object. -T} -NLM_F_EXCL:T{ -Don't replace if the object already exists. -T} -NLM_F_CREATE:T{ -Create object if it doesn't already exist. -T} -NLM_F_APPEND:T{ -Add to the end of the object list. -T} -.TE -.P -.I nlmsg_seq -and -.I nlmsg_pid -are used to track messages. -.I nlmsg_pid -shows the origin of the message. -Note that there isn't a 1:1 relationship between -.I nlmsg_pid -and the PID of the process if the message originated from a netlink -socket. -See the -.B ADDRESS FORMATS -section for further information. -.P -Both -.I nlmsg_seq -and -.I nlmsg_pid -.\" FIXME Explain more about nlmsg_seq and nlmsg_pid. -are opaque to netlink core. -.P -Netlink is not a reliable protocol. -It tries its best to deliver a message to its destination(s), -but may drop messages when an out-of-memory condition or -other error occurs. -For reliable transfer the sender can request an -acknowledgement from the receiver by setting the -.B NLM_F_ACK -flag. -An acknowledgement is an -.B NLMSG_ERROR -packet with the error field set to 0. -The application must generate acknowledgements for -received messages itself. -The kernel tries to send an -.B NLMSG_ERROR -message for every failed packet. -A user process should follow this convention too. -.P -However, reliable transmissions from kernel to user are impossible -in any case. -The kernel can't send a netlink message if the socket buffer is full: -the message will be dropped and the kernel and the user-space process will -no longer have the same view of kernel state. -It is up to the application to detect when this happens (via the -.B ENOBUFS -error returned by -.BR recvmsg (2)) -and resynchronize. -.SS Address formats -The -.I sockaddr_nl -structure describes a netlink client in user space or in the kernel. -A -.I sockaddr_nl -can be either unicast (only sent to one peer) or sent to -netlink multicast groups -.RI ( nl_groups -not equal 0). -.P -.in +4n -.EX -struct sockaddr_nl { - sa_family_t nl_family; /* AF_NETLINK */ - unsigned short nl_pad; /* Zero */ - pid_t nl_pid; /* Port ID */ - __u32 nl_groups; /* Multicast groups mask */ -}; -.EE -.in -.P -.I nl_pid -is the unicast address of netlink socket. -It's always 0 if the destination is in the kernel. -For a user-space process, -.I nl_pid -is usually the PID of the process owning the destination socket. -However, -.I nl_pid -identifies a netlink socket, not a process. -If a process owns several netlink -sockets, then -.I nl_pid -can be equal to the process ID only for at most one socket. -There are two ways to assign -.I nl_pid -to a netlink socket. -If the application sets -.I nl_pid -before calling -.BR bind (2), -then it is up to the application to make sure that -.I nl_pid -is unique. -If the application sets it to 0, the kernel takes care of assigning it. -The kernel assigns the process ID to the first netlink socket the process -opens and assigns a unique -.I nl_pid -to every netlink socket that the process subsequently creates. -.P -.I nl_groups -is a bit mask with every bit representing a netlink group number. -Each netlink family has a set of 32 multicast groups. -When -.BR bind (2) -is called on the socket, the -.I nl_groups -field in the -.I sockaddr_nl -should be set to a bit mask of the groups which it wishes to listen to. -The default value for this field is zero which means that no multicasts -will be received. -A socket may multicast messages to any of the multicast groups by setting -.I nl_groups -to a bit mask of the groups it wishes to send to when it calls -.BR sendmsg (2) -or does a -.BR connect (2). -Only processes with an effective UID of 0 or the -.B CAP_NET_ADMIN -capability may send or listen to a netlink multicast group. -Since Linux 2.6.13, -.\" commit d629b836d151d43332492651dd841d32e57ebe3b -messages can't be broadcast to multiple groups. -Any replies to a message received for a multicast group should be -sent back to the sending PID and the multicast group. -Some Linux kernel subsystems may additionally allow other users -to send and/or receive messages. -As at Linux 3.0, the -.BR NETLINK_KOBJECT_UEVENT , -.BR NETLINK_GENERIC , -.BR NETLINK_ROUTE , -and -.B NETLINK_SELINUX -groups allow other users to receive messages. -No groups allow other users to send messages. -.SS Socket options -To set or get a netlink socket option, call -.BR getsockopt (2) -to read or -.BR setsockopt (2) -to write the option with the option level argument set to -.BR SOL_NETLINK . -Unless otherwise noted, -.I optval -is a pointer to an -.IR int . -.TP -.BR NETLINK_PKTINFO " (since Linux 2.6.14)" -.\" commit 9a4595bc7e67962f13232ee55a64e063062c3a99 -.\" Author: Patrick McHardy <kaber@trash.net> -Enable -.B nl_pktinfo -control messages for received packets to get the extended -destination group number. -.TP -.B NETLINK_ADD_MEMBERSHIP -.TQ -.BR NETLINK_DROP_MEMBERSHIP " (since Linux 2.6.14)" -.\" commit 9a4595bc7e67962f13232ee55a64e063062c3a99 -.\" Author: Patrick McHardy <kaber@trash.net> -Join/leave a group specified by -.IR optval . -.TP -.BR NETLINK_LIST_MEMBERSHIPS " (since Linux 4.2)" -.\" commit b42be38b2778eda2237fc759e55e3b698b05b315 -.\" Author: David Herrmann <dh.herrmann@gmail.com> -Retrieve all groups a socket is a member of. -.I optval -is a pointer to -.B __u32 -and -.I optlen -is the size of the array. -The array is filled with the full membership set of the -socket, and the required array size is returned in -.IR optlen . -.TP -.BR NETLINK_BROADCAST_ERROR " (since Linux 2.6.30)" -.\" commit be0c22a46cfb79ab2342bb28fde99afa94ef868e -.\" Author: Pablo Neira Ayuso <pablo@netfilter.org> -When not set, -.B netlink_broadcast() -only reports -.B ESRCH -errors and silently ignore -.B ENOBUFS -errors. -.TP -.BR NETLINK_NO_ENOBUFS " (since Linux 2.6.30)" -.\" commit 38938bfe3489394e2eed5e40c9bb8f66a2ce1405 -.\" Author: Pablo Neira Ayuso <pablo@netfilter.org> -This flag can be used by unicast and broadcast listeners to avoid receiving -.B ENOBUFS -errors. -.TP -.BR NETLINK_LISTEN_ALL_NSID " (since Linux 4.2)" -.\" commit 59324cf35aba5336b611074028777838a963d03b -.\" Author: Nicolas Dichtel <nicolas.dichtel@6wind.com> -When set, this socket will receive netlink notifications from -all network namespaces that have an -.I nsid -assigned into the network namespace where the socket has been opened. -The -.I nsid -is sent to user space via an ancillary data. -.TP -.BR NETLINK_CAP_ACK " (since Linux 4.3)" -.\" commit 0a6a3a23ea6efde079a5b77688541a98bf202721 -.\" Author: Christophe Ricard <christophe.ricard@gmail.com> -The kernel may fail to allocate the necessary room for the acknowledgement -message back to user space. -This option trims off the payload of the original netlink message. -The netlink message header is still included, so the user can guess from the -sequence number which message triggered the acknowledgement. -.SH VERSIONS -The socket interface to netlink first appeared Linux 2.2. -.P -Linux 2.0 supported a more primitive device-based netlink interface -(which is still available as a compatibility option). -This obsolete interface is not described here. -.SH NOTES -It is often better to use netlink via -.I libnetlink -or -.I libnl -than via the low-level kernel interface. -.SH BUGS -This manual page is not complete. -.SH EXAMPLES -The following example creates a -.B NETLINK_ROUTE -netlink socket which will listen to the -.B RTMGRP_LINK -(network interface create/delete/up/down events) and -.B RTMGRP_IPV4_IFADDR -(IPv4 addresses add/delete events) multicast groups. -.P -.in +4n -.EX -struct sockaddr_nl sa; -\& -memset(&sa, 0, sizeof(sa)); -sa.nl_family = AF_NETLINK; -sa.nl_groups = RTMGRP_LINK | RTMGRP_IPV4_IFADDR; -\& -fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE); -bind(fd, (struct sockaddr *) &sa, sizeof(sa)); -.EE -.in -.P -The next example demonstrates how to send a netlink message to the -kernel (pid 0). -Note that the application must take care of message sequence numbers -in order to reliably track acknowledgements. -.P -.in +4n -.EX -struct nlmsghdr *nh; /* The nlmsghdr with payload to send */ -struct sockaddr_nl sa; -struct iovec iov = { nh, nh\->nlmsg_len }; -struct msghdr msg; -\& -msg = { &sa, sizeof(sa), &iov, 1, NULL, 0, 0 }; -memset(&sa, 0, sizeof(sa)); -sa.nl_family = AF_NETLINK; -nh\->nlmsg_pid = 0; -nh\->nlmsg_seq = ++sequence_number; -/* Request an ack from kernel by setting NLM_F_ACK */ -nh\->nlmsg_flags |= NLM_F_ACK; -\& -sendmsg(fd, &msg, 0); -.EE -.in -.P -And the last example is about reading netlink message. -.P -.in +4n -.EX -int len; -/* 8192 to avoid message truncation on platforms with - page size > 4096 */ -struct nlmsghdr buf[8192/sizeof(struct nlmsghdr)]; -struct iovec iov = { buf, sizeof(buf) }; -struct sockaddr_nl sa; -struct msghdr msg; -struct nlmsghdr *nh; -\& -msg = { &sa, sizeof(sa), &iov, 1, NULL, 0, 0 }; -len = recvmsg(fd, &msg, 0); -\& -for (nh = (struct nlmsghdr *) buf; NLMSG_OK (nh, len); - nh = NLMSG_NEXT (nh, len)) { - /* The end of multipart message */ - if (nh\->nlmsg_type == NLMSG_DONE) - return; -\& - if (nh\->nlmsg_type == NLMSG_ERROR) - /* Do some error handling */ - ... -\& - /* Continue with parsing payload */ - ... -} -.EE -.in -.SH SEE ALSO -.BR cmsg (3), -.BR netlink (3), -.BR capabilities (7), -.BR rtnetlink (7), -.BR sock_diag (7) -.P -.UR ftp://ftp.inr.ac.ru\:/ip\-routing\:/iproute2* -information about libnetlink -.UE -.P -.UR http://www.infradead.org\:/\[ti]tgr\:/libnl/ -information about libnl -.UE -.P -RFC 3549 "Linux Netlink as an IP Services Protocol" |