/*
 * linux/fs/nfs/nfs4namespace.c
 *
 * Copyright (C) 2005 Trond Myklebust <Trond.Myklebust@netapp.com>
 *
 * NFSv4 namespace
 */

#include <linux/config.h>

#include <linux/dcache.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/nfs_fs.h>
#include <linux/string.h>
#include <linux/sunrpc/clnt.h>
#include <linux/vfs.h>
#include <linux/inet.h>
#include "internal.h"

#define NFSDBG_FACILITY		NFSDBG_VFS

/*
 * Check if fs_root is valid
 */
static inline char *nfs4_pathname_string(struct nfs4_pathname *pathname,
					 char *buffer, ssize_t buflen)
{
	char *end = buffer + buflen;
	int n;

	*--end = '\0';
	buflen--;

	n = pathname->ncomponents;
	while (--n >= 0) {
		struct nfs4_string *component = &pathname->components[n];
		buflen -= component->len + 1;
		if (buflen < 0)
			goto Elong;
		end -= component->len;
		memcpy(end, component->data, component->len);
		*--end = '/';
	}
	return end;
Elong:
	return ERR_PTR(-ENAMETOOLONG);
}


/**
 * nfs_follow_referral - set up mountpoint when hitting a referral on moved error
 * @mnt_parent - mountpoint of parent directory
 * @dentry - parent directory
 * @fspath - fs path returned in fs_locations
 * @mntpath - mount path to new server
 * @hostname - hostname of new server
 * @addr - host addr of new server
 *
 */
static struct vfsmount *nfs_follow_referral(const struct vfsmount *mnt_parent,
					    const struct dentry *dentry,
					    struct nfs4_fs_locations *locations)
{
	struct vfsmount *mnt = ERR_PTR(-ENOENT);
	struct nfs_clone_mount mountdata = {
		.sb = mnt_parent->mnt_sb,
		.dentry = dentry,
		.authflavor = NFS_SB(mnt_parent->mnt_sb)->client->cl_auth->au_flavor,
	};
	char *page, *page2;
	char *path, *fs_path;
	char *devname;
	int loc, s;

	if (locations == NULL || locations->nlocations <= 0)
		goto out;

	dprintk("%s: referral at %s/%s\n", __FUNCTION__,
		dentry->d_parent->d_name.name, dentry->d_name.name);

	/* Ensure fs path is a prefix of current dentry path */
	page = (char *) __get_free_page(GFP_USER);
	if (page == NULL)
		goto out;
	page2 = (char *) __get_free_page(GFP_USER);
	if (page2 == NULL)
		goto out;

	path = nfs4_path(dentry, page, PAGE_SIZE);
	if (IS_ERR(path))
		goto out_free;

	fs_path = nfs4_pathname_string(&locations->fs_path, page2, PAGE_SIZE);
	if (IS_ERR(fs_path))
		goto out_free;

	if (strncmp(path, fs_path, strlen(fs_path)) != 0) {
		dprintk("%s: path %s does not begin with fsroot %s\n", __FUNCTION__, path, fs_path);
		goto out_free;
	}

	devname = nfs_devname(mnt_parent, dentry, page, PAGE_SIZE);
	if (IS_ERR(devname)) {
		mnt = (struct vfsmount *)devname;
		goto out_free;
	}

	loc = 0;
	while (loc < locations->nlocations && IS_ERR(mnt)) {
		struct nfs4_fs_location *location = &locations->locations[loc];
		char *mnt_path;

		if (location == NULL || location->nservers <= 0 ||
		    location->rootpath.ncomponents == 0) {
			loc++;
			continue;
		}

		mnt_path = nfs4_pathname_string(&location->rootpath, page2, PAGE_SIZE);
		if (IS_ERR(mnt_path)) {
			loc++;
			continue;
		}
		mountdata.mnt_path = mnt_path;

		s = 0;
		while (s < location->nservers) {
			struct sockaddr_in addr = {};

			if (location->servers[s].len <= 0 ||
			    valid_ipaddr4(location->servers[s].data) < 0) {
				s++;
				continue;
			}

			mountdata.hostname = location->servers[s].data;
			addr.sin_addr.s_addr = in_aton(mountdata.hostname);
			addr.sin_family = AF_INET;
			addr.sin_port = htons(NFS_PORT);
			mountdata.addr = &addr;

			mnt = vfs_kern_mount(&nfs_referral_nfs4_fs_type, 0, devname, &mountdata);
			if (!IS_ERR(mnt)) {
				break;
			}
			s++;
		}
		loc++;
	}

out_free:
	free_page((unsigned long)page);
	free_page((unsigned long)page2);
out:
	dprintk("%s: done\n", __FUNCTION__);
	return mnt;
}

/*
 * nfs_do_refmount - handle crossing a referral on server
 * @dentry - dentry of referral
 * @nd - nameidata info
 *
 */
struct vfsmount *nfs_do_refmount(const struct vfsmount *mnt_parent, struct dentry *dentry)
{
	struct vfsmount *mnt = ERR_PTR(-ENOENT);
	struct dentry *parent;
	struct nfs4_fs_locations *fs_locations = NULL;
	struct page *page;
	int err;

	/* BUG_ON(IS_ROOT(dentry)); */
	dprintk("%s: enter\n", __FUNCTION__);

	page = alloc_page(GFP_KERNEL);
	if (page == NULL)
		goto out;

	fs_locations = kmalloc(sizeof(struct nfs4_fs_locations), GFP_KERNEL);
	if (fs_locations == NULL)
		goto out_free;

	/* Get locations */
	parent = dget_parent(dentry);
	dprintk("%s: getting locations for %s/%s\n", __FUNCTION__, parent->d_name.name, dentry->d_name.name);
	err = nfs4_proc_fs_locations(parent->d_inode, dentry, fs_locations, page);
	dput(parent);
	if (err != 0 || fs_locations->nlocations <= 0 ||
	    fs_locations->fs_path.ncomponents <= 0)
		goto out_free;

	mnt = nfs_follow_referral(mnt_parent, dentry, fs_locations);
out_free:
	__free_page(page);
	kfree(fs_locations);
out:
	dprintk("%s: done\n", __FUNCTION__);
	return mnt;
}