Control flow when running one of:
ip link show
ip link show eth0
ip link set eth0 up
ip link set eth0 down
Links:
Issues:
iplink.c
redefines iplink_req
for no reason (line 218)HAVE_LIBMNL
for error support.From ip/ip_common.h:
struct iplink_req { struct nlmsghdr n; struct ifinfomsg i; char buf[1024]; };
From include/uapi/linux/rtnetlink.h:
/* struct ifinfomsg * passes link level specific information, not dependent * on network protocol. */ struct ifinfomsg { unsigned char ifi_family; unsigned char __ifi_pad; unsigned short ifi_type; /* ARPHRD_* */ int ifi_index; /* Link index */ unsigned ifi_flags; /* IFF_* flags */ unsigned ifi_change; /* IFF_* change mask */ };
From include/uapi/linux/if.h:
enum net_device_flags { /* for compatibility with glibc net/if.h */ #if __UAPI_DEF_IF_NET_DEVICE_FLAGS IFF_UP = 1<<0, /* sysfs */ IFF_BROADCAST = 1<<1, /* volatile */ IFF_DEBUG = 1<<2, /* sysfs */ IFF_LOOPBACK = 1<<3, /* volatile */ IFF_POINTOPOINT = 1<<4, /* volatile */ IFF_NOTRAILERS = 1<<5, /* sysfs */ IFF_RUNNING = 1<<6, /* volatile */ IFF_NOARP = 1<<7, /* sysfs */ IFF_PROMISC = 1<<8, /* sysfs */ IFF_ALLMULTI = 1<<9, /* sysfs */ IFF_MASTER = 1<<10, /* volatile */ IFF_SLAVE = 1<<11, /* volatile */ IFF_MULTICAST = 1<<12, /* sysfs */ IFF_PORTSEL = 1<<13, /* sysfs */ IFF_AUTOMEDIA = 1<<14, /* sysfs */ IFF_DYNAMIC = 1<<15, /* sysfs */ #endif /* __UAPI_DEF_IF_NET_DEVICE_FLAGS */ #if __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO IFF_LOWER_UP = 1<<16, /* volatile */ IFF_DORMANT = 1<<17, /* volatile */ IFF_ECHO = 1<<18, /* volatile */ #endif /* __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO */ };
NAME ip-link - network device configuration SYNOPSIS ip link { COMMAND | help } ip link add [ link DEVICE ] [ name ] NAME [ txqueuelen PACKETS ] [ address LLADDR ] [ broadcast LLADDR ] [ mtu MTU ] [ index IDX ] [ numtxqueues QUEUE_COUNT ] [ numrxqueues QUEUE_COUNT ] [ gso_max_size BYTES ] [ gso_max_segs SEGMENTS ] type TYPE [ ARGS ] ip link delete { DEVICE | group GROUP } type TYPE [ ARGS ] ip link set { DEVICE | group GROUP } [ { up | down } ] [ type ETYPE TYPE_ARGS ] [ arp { on | off } ] [ dynamic { on | off } ] [ multicast { on | off } ] [ allmulticast { on | off } ] [ promisc { on | off } ] [ protodown { on | off } ] [ trailers { on | off } ] [ txqueuelen PACKETS ] [ name NEWNAME ] [ address LLADDR ] [ broadcast LLADDR ] [ mtu MTU ] [ netns { PID | NETNSNAME } ] [ link-netnsid ID ] [ alias NAME ] [ vf NUM [ mac LLADDR ] [ VFVLAN-LIST ] [ rate TXRATE ] [ max_tx_rate TXRATE ] [ min_tx_rate TXRATE ] [ spoofchk { on | off } ] [ query_rss { on | off } ] [ state { auto | enable | disable } ] [ trust { on | off } ] [ node_guid eui64 ] [ port_guid eui64 ] ] [ { xdp | xdpgeneric | xdpdrv | xdpoffload } { off | object FILE [ section NAME ] [ verbose ] | pinned FILE } ] [ master DEVICE ] [ nomaster ] [ vrf NAME ] [ addrgenmode { eui64 | none | stable_secret | random } ] [ macaddr { flush | { add | del } MACADDR | set [ MACADDR [ MACADDR [ ... ] ] ] } ] ip link show [ DEVICE | group GROUP ] [ up ] [ master DEVICE ] [ type ETYPE ] [ vrf NAME ] ip link xstats type TYPE [ ARGS ] ip link afstats [ dev DEVICE ] ip link help [ TYPE ] TYPE := [ bridge | bond | can | dummy | hsr | ifb | ipoib | macvlan | macvtap | vcan | vxcan | veth | vlan | vxlan | ip6tnl | ipip | sit | gre | gretap | erspan | ip6gre | ip6gretap | ip6erspan | vti | nlmon | ipvlan | lowpan | geneve | vrf | macsec | netdevsim | rmnet ] ETYPE := [ TYPE | bridge_slave | bond_slave ] VFVLAN-LIST := [ VFVLAN-LIST ] VFVLAN VFVLAN := [ vlan VLANID [ qos VLAN-QOS ] [ proto VLAN-PROTO ] ]
int do_iplink(int argc, char **argv) { if (argc < 1) return ipaddr_list_link(0, NULL); if (iplink_have_newlink()) { if (matches(*argv, "add") == 0) return iplink_modify(RTM_NEWLINK, NLM_F_CREATE|NLM_F_EXCL, argc-1, argv+1); if (matches(*argv, "set") == 0 || matches(*argv, "change") == 0) return iplink_modify(RTM_NEWLINK, 0, argc-1, argv+1); if (matches(*argv, "replace") == 0) return iplink_modify(RTM_NEWLINK, NLM_F_CREATE|NLM_F_REPLACE, argc-1, argv+1); if (matches(*argv, "delete") == 0) return iplink_modify(RTM_DELLINK, 0, argc-1, argv+1); } else { #if IPLINK_IOCTL_COMPAT if (matches(*argv, "set") == 0) return do_set(argc-1, argv+1); #endif ... snip ...
Modify the appropriate flags:
static int do_set(int argc, char **argv) { char *dev = NULL; __u32 mask = 0; __u32 flags = 0; int qlen = -1; int mtu = -1; char *newaddr = NULL; char *newbrd = NULL; struct ifreq ifr0, ifr1; char *newname = NULL; int htype, halen; while (argc > 0) { if (strcmp(*argv, "up") == 0) { mask |= IFF_UP; flags |= IFF_UP; } else if (strcmp(*argv, "down") == 0) { mask |= IFF_UP; flags &= ~IFF_UP; ... snip ... if (mask) return do_chflags(dev, flags, mask); return 0; }
static int do_chflags(const char *dev, __u32 flags, __u32 mask) { struct ifreq ifr; int fd; int err; strlcpy(ifr.ifr_name, dev, IFNAMSIZ); fd = get_ctl_fd(); if (fd < 0) return -1; err = ioctl(fd, SIOCGIFFLAGS, &ifr); if (err) { perror("SIOCGIFFLAGS"); close(fd); return -1; } if ((ifr.ifr_flags^flags)&mask) { ifr.ifr_flags &= ~mask; ifr.ifr_flags |= mask&flags; err = ioctl(fd, SIOCSIFFLAGS, &ifr); if (err) perror("SIOCSIFFLAGS"); } close(fd); return err; }
static const struct file_operations socket_file_ops = { .owner = THIS_MODULE, .llseek = no_llseek, .read_iter = sock_read_iter, .write_iter = sock_write_iter, .poll = sock_poll, .unlocked_ioctl = sock_ioctl, #ifdef CONFIG_COMPAT .compat_ioctl = compat_sock_ioctl, #endif .mmap = sock_mmap, .release = sock_close, .fasync = sock_fasync, .sendpage = sock_sendpage, .splice_write = generic_splice_sendpage, .splice_read = sock_splice_read, };
static long sock_ioctl(struct file *file, unsigned cmd, unsigned long arg) { struct socket *sock; struct sock *sk; void __user *argp = (void __user *)arg; int pid, err; struct net *net; sock = file->private_data; sk = sock->sk; net = sock_net(sk); ... snip ... default: err = sock_do_ioctl(net, sock, cmd, arg, sizeof(struct ifreq)); break; } return err; }
static long sock_do_ioctl(struct net *net, struct socket *sock, unsigned int cmd, unsigned long arg, unsigned int ifreq_size) { int err; void __user *argp = (void __user *)arg; err = sock->ops->ioctl(sock, cmd, arg); /* * If this ioctl is unknown try to hand it down * to the NIC driver. */ if (err != -ENOIOCTLCMD) return err; if (cmd == SIOCGIFCONF) { struct ifconf ifc; if (copy_from_user(&ifc, argp, sizeof(struct ifconf))) return -EFAULT; rtnl_lock(); err = dev_ifconf(net, &ifc, sizeof(struct ifreq)); rtnl_unlock(); if (!err && copy_to_user(argp, &ifc, sizeof(struct ifconf))) err = -EFAULT; } else { struct ifreq ifr; bool need_copyout; if (copy_from_user(&ifr, argp, ifreq_size)) return -EFAULT; err = dev_ioctl(net, cmd, &ifr, &need_copyout); if (!err && need_copyout) if (copy_to_user(argp, &ifr, ifreq_size)) return -EFAULT; } return err; }
From include/uapi/linux/if.h:
/* for compatibility with glibc net/if.h */ #if __UAPI_DEF_IF_IFREQ struct ifreq { #define IFHWADDRLEN 6 union { char ifrn_name[IFNAMSIZ]; /* if name, e.g. "en0" */ } ifr_ifrn; union { struct sockaddr ifru_addr; struct sockaddr ifru_dstaddr; struct sockaddr ifru_broadaddr; struct sockaddr ifru_netmask; struct sockaddr ifru_hwaddr; short ifru_flags; int ifru_ivalue; int ifru_mtu; struct ifmap ifru_map; char ifru_slave[IFNAMSIZ]; /* Just fits the size */ char ifru_newname[IFNAMSIZ]; void __user * ifru_data; struct if_settings ifru_settings; } ifr_ifru; }; #endif /* __UAPI_DEF_IF_IFREQ */ #define ifr_name ifr_ifrn.ifrn_name /* interface name */ #define ifr_hwaddr ifr_ifru.ifru_hwaddr /* MAC address */ #define ifr_addr ifr_ifru.ifru_addr /* address */ #define ifr_dstaddr ifr_ifru.ifru_dstaddr /* other end of p-p lnk */ #define ifr_broadaddr ifr_ifru.ifru_broadaddr /* broadcast address */ #define ifr_netmask ifr_ifru.ifru_netmask /* interface net mask */ #define ifr_flags ifr_ifru.ifru_flags /* flags */ #define ifr_metric ifr_ifru.ifru_ivalue /* metric */ #define ifr_mtu ifr_ifru.ifru_mtu /* mtu */ #define ifr_map ifr_ifru.ifru_map /* device map */ #define ifr_slave ifr_ifru.ifru_slave /* slave device */ #define ifr_data ifr_ifru.ifru_data /* for use by interface */ #define ifr_ifindex ifr_ifru.ifru_ivalue /* interface index */ #define ifr_bandwidth ifr_ifru.ifru_ivalue /* link bandwidth */ #define ifr_qlen ifr_ifru.ifru_ivalue /* Queue length */ #define ifr_newname ifr_ifru.ifru_newname /* New name */ #define ifr_settings ifr_ifru.ifru_settings /* Device/proto settings*/
int dev_ioctl(struct net *net, unsigned int cmd, struct ifreq *ifr, bool *need_copyout) { ... snip ... switch (cmd) { /* * These ioctl calls: * - can be done by all. * - atomic and do not require locking. * - return a value */ case SIOCGIFFLAGS: case SIOCGIFMETRIC: case SIOCGIFMTU: case SIOCGIFHWADDR: case SIOCGIFSLAVE: case SIOCGIFMAP: case SIOCGIFINDEX: case SIOCGIFTXQLEN: dev_load(net, ifr->ifr_name); rcu_read_lock(); ret = dev_ifsioc_locked(net, ifr, cmd); rcu_read_unlock(); if (colon) *colon = ':'; return ret; ... snip ... case SIOCSIFFLAGS: case SIOCSIFMETRIC: case SIOCSIFMTU: case SIOCSIFHWADDR: case SIOCSIFSLAVE: case SIOCADDMULTI: case SIOCDELMULTI: case SIOCSIFHWBROADCAST: case SIOCSMIIREG: case SIOCBONDENSLAVE: case SIOCBONDRELEASE: case SIOCBONDSETHWADDR: case SIOCBONDCHANGEACTIVE: case SIOCBRADDIF: case SIOCBRDELIF: case SIOCSHWTSTAMP: if (!ns_capable(net->user_ns, CAP_NET_ADMIN)) return -EPERM; /* fall through */ case SIOCBONDSLAVEINFOQUERY: case SIOCBONDINFOQUERY: dev_load(net, ifr->ifr_name); rtnl_lock(); ret = dev_ifsioc(net, ifr, cmd); rtnl_unlock(); if (need_copyout) *need_copyout = false; return ret;
static int dev_ifsioc(struct net *net, struct ifreq *ifr, unsigned int cmd) { int err; struct net_device *dev = __dev_get_by_name(net, ifr->ifr_name); const struct net_device_ops *ops; if (!dev) return -ENODEV; ops = dev->netdev_ops; switch (cmd) { case SIOCSIFFLAGS: /* Set interface flags */ return dev_change_flags(dev, ifr->ifr_flags);
int dev_change_flags(struct net_device *dev, unsigned int flags) { int ret; unsigned int changes, old_flags = dev->flags, old_gflags = dev->gflags; ret = __dev_change_flags(dev, flags); if (ret < 0) return ret; changes = (old_flags ^ dev->flags) | (old_gflags ^ dev->gflags); __dev_notify_flags(dev, old_flags, changes); return ret; }
int __dev_change_flags(struct net_device *dev, unsigned int flags) { unsigned int old_flags = dev->flags; int ret; ASSERT_RTNL(); /* * Set the flags on our device. */ dev->flags = (flags & (IFF_DEBUG | IFF_NOTRAILERS | IFF_NOARP | IFF_DYNAMIC | IFF_MULTICAST | IFF_PORTSEL | IFF_AUTOMEDIA)) | (dev->flags & (IFF_UP | IFF_VOLATILE | IFF_PROMISC | IFF_ALLMULTI)); ... snip ... ret = 0; if ((old_flags ^ flags) & IFF_UP) { if (old_flags & IFF_UP) __dev_close(dev); else ret = __dev_open(dev); }