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ipp_up_and_iff_running [2018/08/25 16:15]
rpjday [Up but disconnected]
ipp_up_and_iff_running [2018/08/27 08:20]
rpjday [Up, then disconnected]
Line 8: Line 8:
  
 ===== Flags ===== ===== Flags =====
 +
 +Issues:
 +
 +  * Is ''​IFF_LOWER_UP''​ significant?​
 +  * Can we use ''​IFF_DEBUG''?​
 +  * Understand actual meaning of "​volatile"​.
  
 From ''​include/​uapi/​linux/​if.h'':​ From ''​include/​uapi/​linux/​if.h'':​
  
 <​code>​ <​code>​
 +/**
 + * enum net_device_flags - &struct net_device flags
 + *
 + * These are the &struct net_device flags, they can be set by drivers, the
 + * kernel and some can be triggered by userspace. Userspace can query and
 + * set these flags using userspace utilities but there is also a sysfs
 + * entry available for all dev flags which can be queried and set. These flags
 + * are shared for all types of net_devices. The sysfs entries are available
 + * via /​sys/​class/​net/<​dev>/​flags. Flags which can be toggled through sysfs
 + * are annotated below, note that only a few flags can be toggled and some
 + * other flags are always preserved from the original net_device flags
 + * even if you try to set them via sysfs. Flags which are always preserved
 + * are kept under the flag grouping @IFF_VOLATILE. Flags which are volatile
 + * are annotated below as such.
 + *
 + * You should have a pretty good reason to be extending these flags.
 + *
 + * @IFF_UP: interface is up. Can be toggled through sysfs.
 + * @IFF_BROADCAST:​ broadcast address valid. Volatile.
 + * @IFF_DEBUG: turn on debugging. Can be toggled through sysfs.
 + * @IFF_LOOPBACK:​ is a loopback net. Volatile.
 + * @IFF_POINTOPOINT:​ interface is has p-p link. Volatile.
 + * @IFF_NOTRAILERS:​ avoid use of trailers. Can be toggled through sysfs.
 + ​* ​     Volatile.
 + * @IFF_RUNNING:​ interface RFC2863 OPER_UP. Volatile.
 + * @IFF_NOARP: no ARP protocol. Can be toggled through sysfs. Volatile.
 + * @IFF_PROMISC:​ receive all packets. Can be toggled through sysfs.
 + * @IFF_ALLMULTI:​ receive all multicast packets. Can be toggled through
 + ​* ​     sysfs.
 + * @IFF_MASTER:​ master of a load balancer. Volatile.
 + * @IFF_SLAVE: slave of a load balancer. Volatile.
 + * @IFF_MULTICAST:​ Supports multicast. Can be toggled through sysfs.
 + * @IFF_PORTSEL:​ can set media type. Can be toggled through sysfs.
 + * @IFF_AUTOMEDIA:​ auto media select active. Can be toggled through sysfs.
 + * @IFF_DYNAMIC:​ dialup device with changing addresses. Can be toggled
 + ​* ​     through sysfs.
 + * @IFF_LOWER_UP:​ driver signals L1 up. Volatile.
 + * @IFF_DORMANT:​ driver signals dormant. Volatile.
 + * @IFF_ECHO: echo sent packets. Volatile.
 + */
 +
 enum net_device_flags { enum net_device_flags {
 /* for compatibility with glibc net/if.h */ /* for compatibility with glibc net/if.h */
Line 65: Line 112:
  
 ===== Flags ===== ===== Flags =====
 +
 +==== Source ====
 +
 +''​ifconfig''​ is getting hex value from ''​SIOCGIFFLAGS''​ which does ''​dev_get_flags(dev)''​.
  
 ==== Up and running ==== ==== Up and running ====
Line 93: Line 144:
         RX errors 0  dropped 0  overruns 0  frame 0         RX errors 0  dropped 0  overruns 0  frame 0
         TX packets 36836  bytes 9042100 (8.6 MiB)         TX packets 36836  bytes 9042100 (8.6 MiB)
 +        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
 +</​code>​
 +
 +==== Up again ====
 +
 +UP, shortly followed by RUNNING:
 +
 +<​code>​
 +enp3s0: flags=4163<​UP,​BROADCAST,​RUNNING,​MULTICAST> ​ mtu 1500
 +        inet 192.168.0.15 ​ netmask 255.255.255.0 ​ broadcast 192.168.0.255
 +        inet6 fd00:​f81d:​f81:​4062:​2e56:​dcff:​fe25:​ad47 ​ prefixlen 64  scopeid 0x0<​global>​
 +        inet6 fe80::​2e56:​dcff:​fe25:​ad47 ​ prefixlen 64  scopeid 0x20<​link>​
 +        ether 2c:​56:​dc:​25:​ad:​47 ​ txqueuelen 1000  (Ethernet)
 +        RX packets 1268514 ​ bytes 1611028865 (1.5 GiB)
 +        RX errors 0  dropped 0  overruns 0  frame 0
 +        TX packets 396222 ​ bytes 65965632 (62.9 MiB)
         TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0         TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
 </​code>​ </​code>​
Line 110: Line 177:
         TX packets 36917  bytes 9052750 (8.6 MiB)         TX packets 36917  bytes 9052750 (8.6 MiB)
         TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0         TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
 +</​code>​
 +
 +===== dev_get_flags() =====
 +
 +==== net/​core/​dev_ioctl.c ====
 +
 +This is how ''​ifconfig''​ gets its info -- via ''​dev_get_flags()'':​
 +
 +<​code>​
 +/*
 + ​* ​     Perform the SIOCxIFxxx calls, inside rcu_read_lock()
 + */
 +static int dev_ifsioc_locked(struct net *net, struct ifreq *ifr, unsigned int cmd)
 +{
 +        int err;
 +        struct net_device *dev = dev_get_by_name_rcu(net,​ ifr->​ifr_name);​
 +
 +        if (!dev)
 +                return -ENODEV;
 +
 +        switch (cmd) {
 +        case SIOCGIFFLAGS: ​     /* Get interface flags */
 +                ifr->​ifr_flags = (short) dev_get_flags(dev);​
 +                return 0;
 +</​code>​
 +
 +==== net/​core/​dev.c ====
 +
 +Volatile flags are supported via RFC2863 operstates.
 +
 +<​code>​
 +/**
 + ​* dev_get_flags - get flags reported to userspace
 + ​* @dev:​ device
 + *
 + * Get the combination of flag bits exported through APIs to userspace.
 + */
 +unsigned int dev_get_flags(const struct net_device *dev)
 +{
 + unsigned int flags;
 +
 + flags = (dev->​flags & ~(IFF_PROMISC |
 + IFF_ALLMULTI |
 + IFF_RUNNING |
 + IFF_LOWER_UP |
 + IFF_DORMANT)) |
 + (dev->​gflags & (IFF_PROMISC |
 + IFF_ALLMULTI));​
 +
 + if (netif_running(dev)) {
 + if (netif_oper_up(dev))
 + flags |= IFF_RUNNING;​
 + if (netif_carrier_ok(dev))
 + flags |= IFF_LOWER_UP;​
 + if (netif_dormant(dev))
 + flags |= IFF_DORMANT;​
 + }
 +
 + return flags;
 +}
 +EXPORT_SYMBOL(dev_get_flags);​
 </​code>​ </​code>​
ipp_up_and_iff_running.txt ยท Last modified: 2018/08/27 11:03 by rpjday