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--- ip_up_down [2018/10/04 10:05] – [Overview] rpjday
+++ ip_up_down [2018/10/04 11:09] (current) – [__dev_change_flags()] rpjday
@@ Line 15: / Line 15: @@
   * ''iplink.c'' redefines ''iplink_req'' for no reason (line 218)
+  * Define ''HAVE_LIBMNL'' for error support.
 ===== Structures =====
@@ Line 83: / Line 84: @@
 </code>
-==== struct ifreq ====
-From [[https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/uapi/linux/if.h|include/uapi/linux/if.h]]:
-<code>
-/* 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*/
-</code>
 ===== Usage =====
@@ Line 247: / Line 198: @@
 ==== do_set() ====
+Modify the appropriate flags:
 <code>
@@ Line 305: / Line 258: @@
         return err;
 }
+</code>
+===== Sockets and ioctl calls (net/socket.c) =====
+==== socket_file_ops ====
+<code>
+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,
+};
+</code>
+==== sock_ioctl() ====
+<code>
+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;
+}
+</code>
+==== sock_do_ioctl() ====
+<code>
+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;
+}
+</code>
+===== struct ifreq =====
+From [[https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/uapi/linux/if.h|include/uapi/linux/if.h]]:
+<code>
+/* 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*/
 </code>
 ===== net/core/dev_ioctl.c =====
+==== dev_ioctl() ====
+<code>
+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;
+</code>
+==== dev_ifsioc() ====
+<code>
+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);
+</code>
+===== net/core/dev.c =====
+==== dev_change_flags() ====
+<code>
+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;
+}
+</code>
+==== __dev_change_flags() ====
+<code>
+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);
+	}
+</code>