{ "mode": "man", "parameter": "netdevice", "section": "7", "url": "https://www.chedong.com/phpMan.php/man/netdevice/7/json", "generated": "2026-05-30T05:09:57Z", "synopsis": "", "sections": { "NAME": { "content": "netdevice - low-level access to Linux network devices\n", "subsections": [] }, "SYNOPSIS": { "content": "", "subsections": [ { "name": "#include ", "content": "" }, { "name": "#include ", "content": "" } ] }, "DESCRIPTION": { "content": "This man page describes the sockets interface which is used to configure network devices.\n\nLinux supports some standard ioctls to configure network devices. They can be used on any\nsocket's file descriptor regardless of the family or type. Most of them pass an ifreq struc‐\nture:\n\nstruct ifreq {\nchar ifrname[IFNAMSIZ]; /* Interface name */\nunion {\nstruct sockaddr ifraddr;\nstruct sockaddr ifrdstaddr;\nstruct sockaddr ifrbroadaddr;\nstruct sockaddr ifrnetmask;\nstruct sockaddr ifrhwaddr;\nshort ifrflags;\nint ifrifindex;\nint ifrmetric;\nint ifrmtu;\nstruct ifmap ifrmap;\nchar ifrslave[IFNAMSIZ];\nchar ifrnewname[IFNAMSIZ];\nchar *ifrdata;\n};\n};\n\nNormally, the user specifies which device to affect by setting ifrname to the name of the\ninterface. All other members of the structure may share memory.\n", "subsections": [ { "name": "Ioctls", "content": "If an ioctl is marked as privileged, then using it requires an effective user ID of 0 or the\nCAPNETADMIN capability. If this is not the case, EPERM will be returned.\n\nSIOCGIFNAME\nGiven the ifrifindex, return the name of the interface in ifrname. This is the only\nioctl which returns its result in ifrname.\n\nSIOCGIFINDEX\nRetrieve the interface index of the interface into ifrifindex.\n\nSIOCGIFFLAGS, SIOCSIFFLAGS\nGet or set the active flag word of the device. ifrflags contains a bit mask of the\nfollowing values:\n\nDevice flags\nIFFUP Interface is running.\nIFFBROADCAST Valid broadcast address set.\nIFFDEBUG Internal debugging flag.\nIFFLOOPBACK Interface is a loopback interface.\nIFFPOINTOPOINT Interface is a point-to-point link.\nIFFRUNNING Resources allocated.\nIFFNOARP No arp protocol, L2 destination address not\nset.\nIFFPROMISC Interface is in promiscuous mode.\n\nIFFNOTRAILERS Avoid use of trailers.\nIFFALLMULTI Receive all multicast packets.\nIFFMASTER Master of a load balancing bundle.\nIFFSLAVE Slave of a load balancing bundle.\nIFFMULTICAST Supports multicast\nIFFPORTSEL Is able to select media type via ifmap.\nIFFAUTOMEDIA Auto media selection active.\nIFFDYNAMIC The addresses are lost when the interface\ngoes down.\nIFFLOWERUP Driver signals L1 up (since Linux 2.6.17)\nIFFDORMANT Driver signals dormant (since Linux 2.6.17)\nIFFECHO Echo sent packets (since Linux 2.6.25)\n\nSetting the active flag word is a privileged operation, but any process may read it.\n\nSIOCGIFPFLAGS, SIOCSIFPFLAGS\nGet or set extended (private) flags for the device. ifrflags contains a bit mask of\nthe following values:\n\nPrivate flags\nIFF8021QVLAN Interface is 802.1Q VLAN device.\nIFFEBRIDGE Interface is Ethernet bridging device.\nIFFSLAVEINACTIVE Interface is inactive bonding slave.\nIFFMASTER8023AD Interface is 802.3ad bonding master.\nIFFMASTERALB Interface is balanced-alb bonding master.\nIFFBONDING Interface is a bonding master or slave.\nIFFSLAVENEEDARP Interface needs ARPs for validation.\nIFFISATAP Interface is RFC4214 ISATAP interface.\n\nSetting the extended (private) interface flags is a privileged operation.\n\nSIOCGIFADDR, SIOCSIFADDR\nGet or set the address of the device using ifraddr. Setting the interface address is\na privileged operation. For compatibility, only AFINET addresses are accepted or re‐\nturned.\n\nSIOCGIFDSTADDR, SIOCSIFDSTADDR\nGet or set the destination address of a point-to-point device using ifrdstaddr. For\ncompatibility, only AFINET addresses are accepted or returned. Setting the destina‐\ntion address is a privileged operation.\n\nSIOCGIFBRDADDR, SIOCSIFBRDADDR\nGet or set the broadcast address for a device using ifrbrdaddr. For compatibility,\nonly AFINET addresses are accepted or returned. Setting the broadcast address is a\nprivileged operation.\n\nSIOCGIFNETMASK, SIOCSIFNETMASK\nGet or set the network mask for a device using ifrnetmask. For compatibility, only\nAFINET addresses are accepted or returned. Setting the network mask is a privileged\noperation.\n\nSIOCGIFMETRIC, SIOCSIFMETRIC\nGet or set the metric of the device using ifrmetric. This is currently not imple‐\nmented; it sets ifrmetric to 0 if you attempt to read it and returns EOPNOTSUPP if\nyou attempt to set it.\n\nSIOCGIFMTU, SIOCSIFMTU\nGet or set the MTU (Maximum Transfer Unit) of a device using ifrmtu. Setting the MTU\nis a privileged operation. Setting the MTU to too small values may cause kernel\ncrashes.\n\nSIOCGIFHWADDR, SIOCSIFHWADDR\nGet or set the hardware address of a device using ifrhwaddr. The hardware address is\nspecified in a struct sockaddr. safamily contains the ARPHRD* device type, sadata\nthe L2 hardware address starting from byte 0. Setting the hardware address is a priv‐\nileged operation.\n\nSIOCSIFHWBROADCAST\nSet the hardware broadcast address of a device from ifrhwaddr. This is a privileged\noperation.\n\nSIOCGIFMAP, SIOCSIFMAP\nGet or set the interface's hardware parameters using ifrmap. Setting the parameters\nis a privileged operation.\n\nstruct ifmap {\nunsigned long memstart;\nunsigned long memend;\nunsigned short baseaddr;\nunsigned char irq;\nunsigned char dma;\nunsigned char port;\n};\n\nThe interpretation of the ifmap structure depends on the device driver and the archi‐\ntecture.\n\nSIOCADDMULTI, SIOCDELMULTI\nAdd an address to or delete an address from the device's link layer multicast filters\nusing ifrhwaddr. These are privileged operations. See also packet(7) for an alter‐\nnative.\n\nSIOCGIFTXQLEN, SIOCSIFTXQLEN\nGet or set the transmit queue length of a device using ifrqlen. Setting the transmit\nqueue length is a privileged operation.\n\nSIOCSIFNAME\nChanges the name of the interface specified in ifrname to ifrnewname. This is a\nprivileged operation. It is allowed only when the interface is not up.\n\nSIOCGIFCONF\nReturn a list of interface (network layer) addresses. This currently means only ad‐\ndresses of the AFINET (IPv4) family for compatibility. Unlike the others, this ioctl\npasses an ifconf structure:\n\nstruct ifconf {\nint ifclen; /* size of buffer */\nunion {\nchar *ifcbuf; /* buffer address */\nstruct ifreq *ifcreq; /* array of structures */\n};\n};\n\nIf ifcreq is NULL, SIOCGIFCONF returns the necessary buffer size in bytes for receiv‐\ning all available addresses in ifclen. Otherwise, ifcreq contains a pointer to an\narray of ifreq structures to be filled with all currently active L3 interface ad‐\ndresses. ifclen contains the size of the array in bytes. Within each ifreq struc‐\nture, ifrname will receive the interface name, and ifraddr the address. The actual\nnumber of bytes transferred is returned in ifclen.\n\nIf the size specified by ifclen is insufficient to store all the addresses, the ker‐\nnel will skip the exceeding ones and return success. There is no reliable way of de‐\ntecting this condition once it has occurred. It is therefore recommended to either\ndetermine the necessary buffer size beforehand by calling SIOCGIFCONF with ifcreq set\nto NULL, or to retry the call with a bigger buffer whenever ifclen upon return dif‐\nfers by less than sizeof(struct ifreq) from its original value.\n\nIf an error occurs accessing the ifconf or ifreq structures, EFAULT will be returned.\n\nMost protocols support their own ioctls to configure protocol-specific interface options.\nSee the protocol man pages for a description. For configuring IP addresses, see ip(7).\n\nIn addition, some devices support private ioctls. These are not described here.\n" } ] }, "NOTES": { "content": "SIOCGIFCONF and the other ioctls that accept or return only AFINET socket addresses are IP-\nspecific and perhaps should rather be documented in ip(7).\n\nThe names of interfaces with no addresses or that don't have the IFFRUNNING flag set can be\nfound via /proc/net/dev.\n\nLocal IPv6 IP addresses can be found via /proc/net or via rtnetlink(7).\n", "subsections": [] }, "BUGS": { "content": "glibc 2.1 is missing the ifrnewname macro in . Add the following to your program\nas a workaround:\n\n#ifndef ifrnewname\n#define ifrnewname ifrifru.ifruslave\n#endif\n", "subsections": [] }, "SEE ALSO": { "content": "proc(5), capabilities(7), ip(7), rtnetlink(7)\n", "subsections": [] }, "COLOPHON": { "content": "This page is part of release 5.10 of the Linux man-pages project. A description of the\nproject, information about reporting bugs, and the latest version of this page, can be found\nat https://www.kernel.org/doc/man-pages/.\n\n\n\nLinux 2020-08-13 NETDEVICE(7)", "subsections": [] } }, "summary": "netdevice - low-level access to Linux network devices", "flags": [], "examples": [], "see_also": [ { "name": "proc", "section": "5", "url": "https://www.chedong.com/phpMan.php/man/proc/5/json" }, { "name": "capabilities", "section": "7", "url": "https://www.chedong.com/phpMan.php/man/capabilities/7/json" }, { "name": "ip", "section": "7", "url": "https://www.chedong.com/phpMan.php/man/ip/7/json" }, { "name": "rtnetlink", "section": "7", "url": "https://www.chedong.com/phpMan.php/man/rtnetlink/7/json" } ] }