[NETFITLER]: Add nfnetlink layer.

Introduce "nfnetlink" (netfilter netlink) layer.  This layer is used as
transport layer for all userspace communication of the new upcoming
netfilter subsystems, such as ctnetlink, nfnetlink_queue and some day even
the mythical pkttables ;)

Signed-off-by: Harald Welte <laforge@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 349 insertions, 0 deletions

diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig
new file mode 100644
index 000000000000..3629d3d1776d
--- /dev/null
+++ b/net/netfilter/Kconfig
@@ -0,0 +1,5 @@
+config NETFILTER_NETLINK
+       tristate "Netfilter netlink interface"
+       help
+         If this option is enabled, the kernel will include support
+         for the new netfilter netlink interface.
diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
new file mode 100644
index 000000000000..02e67d371941
--- /dev/null
+++ b/net/netfilter/Makefile
@@ -0,0 +1 @@
+obj-$(CONFIG_NETFILTER_NETLINK) += nfnetlink.o
diff --git a/net/netfilter/nfnetlink.c b/net/netfilter/nfnetlink.c
new file mode 100644
index 000000000000..710acd77cc4c
--- /dev/null
+++ b/net/netfilter/nfnetlink.c
@@ -0,0 +1,343 @@
+/* Netfilter messages via netlink socket. Allows for user space
+ * protocol helpers and general trouble making from userspace.
+ *
+ * (C) 2001 by Jay Schulist <jschlst@samba.org>,
+ * (C) 2002-2005 by Harald Welte <laforge@gnumonks.org>
+ * (C) 2005 by Pablo Neira Ayuso <pablo@eurodev.net>
+ *
+ * Initial netfilter messages via netlink development funded and
+ * generally made possible by Network Robots, Inc. (www.networkrobots.com)
+ *
+ * Further development of this code funded by Astaro AG (http://www.astaro.com)
+ *
+ * This software may be used and distributed according to the terms
+ * of the GNU General Public License, incorporated herein by reference.
+ */
+
+#include <linux/config.h>
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/socket.h>
+#include <linux/kernel.h>
+#include <linux/major.h>
+#include <linux/sched.h>
+#include <linux/timer.h>
+#include <linux/string.h>
+#include <linux/sockios.h>
+#include <linux/net.h>
+#include <linux/fcntl.h>
+#include <linux/skbuff.h>
+#include <asm/uaccess.h>
+#include <asm/system.h>
+#include <net/sock.h>
+#include <linux/init.h>
+#include <linux/spinlock.h>
+
+#include <linux/netfilter.h>
+#include <linux/netlink.h>
+#include <linux/netfilter/nfnetlink.h>
+
+MODULE_LICENSE("GPL");
+
+static char __initdata nfversion[] = "0.30";
+
+#if 0
+#define DEBUGP printk
+#else
+#define DEBUGP(format, args...)
+#endif
+
+static struct sock *nfnl = NULL;
+static struct nfnetlink_subsystem *subsys_table[NFNL_SUBSYS_COUNT];
+DECLARE_MUTEX(nfnl_sem);
+
+void nfnl_lock(void)
+{
+        nfnl_shlock();
+}
+
+void nfnl_unlock(void)
+{
+        nfnl_shunlock();
+}
+
+int nfnetlink_subsys_register(struct nfnetlink_subsystem *n)
+{
+        DEBUGP("registering subsystem ID %u\n", n->subsys_id);
+
+        /* If the netlink socket wasn't created, then fail */
+        if (!nfnl)
+                return -1;
+
+        nfnl_lock();
+        subsys_table[n->subsys_id] = n;
+        nfnl_unlock();
+
+        return 0;
+}
+
+int nfnetlink_subsys_unregister(struct nfnetlink_subsystem *n)
+{
+        DEBUGP("unregistering subsystem ID %u\n", n->subsys_id);
+
+        nfnl_lock();
+        subsys_table[n->subsys_id] = NULL;
+        nfnl_unlock();
+
+        return 0;
+}
+
+static inline struct nfnetlink_subsystem *nfnetlink_get_subsys(u_int16_t type)
+{
+        u_int8_t subsys_id = NFNL_SUBSYS_ID(type);
+
+        if (subsys_id >= NFNL_SUBSYS_COUNT
+            || subsys_table[subsys_id] == NULL)
+                return NULL;
+
+        return subsys_table[subsys_id];
+}
+
+static inline struct nfnl_callback *
+nfnetlink_find_client(u_int16_t type, struct nfnetlink_subsystem *ss)
+{
+        u_int8_t cb_id = NFNL_MSG_TYPE(type);
+        
+        if (cb_id >= ss->cb_count) {
+                DEBUGP("msgtype %u >= %u, returning\n", type, ss->cb_count);
+                return NULL;
+        }
+
+        return &ss->cb[cb_id];
+}
+
+void __nfa_fill(struct sk_buff *skb, int attrtype, int attrlen,
+                const void *data)
+{
+        struct nfattr *nfa;
+        int size = NFA_LENGTH(attrlen);
+
+        nfa = (struct nfattr *)skb_put(skb, NFA_ALIGN(size));
+        nfa->nfa_type = attrtype;
+        nfa->nfa_len  = size;
+        memcpy(NFA_DATA(nfa), data, attrlen);
+}
+
+int nfattr_parse(struct nfattr *tb[], int maxattr, struct nfattr *nfa, int len)
+{
+        memset(tb, 0, sizeof(struct nfattr *) * maxattr);
+
+        while (NFA_OK(nfa, len)) {
+                unsigned flavor = nfa->nfa_type;
+                if (flavor && flavor <= maxattr)
+                        tb[flavor-1] = nfa;
+                nfa = NFA_NEXT(nfa, len);
+        }
+
+        return 0;
+}
+
+/**
+ * nfnetlink_check_attributes - check and parse nfnetlink attributes
+ *
+ * subsys: nfnl subsystem for which this message is to be parsed
+ * nlmsghdr: netlink message to be checked/parsed
+ * cda: array of pointers, needs to be at least subsys->attr_count big
+ *
+ */
+static int
+nfnetlink_check_attributes(struct nfnetlink_subsystem *subsys,
+                           struct nlmsghdr *nlh, struct nfattr *cda[])
+{
+        int min_len;
+
+        memset(cda, 0, sizeof(struct nfattr *) * subsys->attr_count);
+
+        /* check attribute lengths. */
+        min_len = NLMSG_ALIGN(sizeof(struct nfgenmsg));
+        if (nlh->nlmsg_len < min_len)
+                return -EINVAL;
+
+        if (nlh->nlmsg_len > min_len) {
+                struct nfattr *attr = NFM_NFA(NLMSG_DATA(nlh));
+                int attrlen = nlh->nlmsg_len - NLMSG_ALIGN(min_len);
+
+                while (NFA_OK(attr, attrlen)) {
+                        unsigned flavor = attr->nfa_type;
+                        if (flavor) {
+                                if (flavor > subsys->attr_count)
+                                        return -EINVAL;
+                                cda[flavor - 1] = attr;
+                        }
+                        attr = NFA_NEXT(attr, attrlen);
+                }
+        } else
+                return -EINVAL;
+
+        return 0;
+}
+
+int nfnetlink_send(struct sk_buff *skb, u32 pid, unsigned group, int echo)
+{
+        int allocation = in_interrupt() ? GFP_ATOMIC : GFP_KERNEL;
+        int err = 0;
+
+        NETLINK_CB(skb).dst_groups = group;
+        if (echo)
+                atomic_inc(&skb->users);
+        netlink_broadcast(nfnl, skb, pid, group, allocation);
+        if (echo)
+                err = netlink_unicast(nfnl, skb, pid, MSG_DONTWAIT);
+
+        return err;
+}
+
+int nfnetlink_unicast(struct sk_buff *skb, u_int32_t pid, int flags)
+{
+        return netlink_unicast(nfnl, skb, pid, flags);
+}
+
+/* Process one complete nfnetlink message. */
+static inline int nfnetlink_rcv_msg(struct sk_buff *skb,
+                                    struct nlmsghdr *nlh, int *errp)
+{
+        struct nfnl_callback *nc;
+        struct nfnetlink_subsystem *ss;
+        int type, err = 0;
+
+        DEBUGP("entered; subsys=%u, msgtype=%u\n",
+                 NFNL_SUBSYS_ID(nlh->nlmsg_type),
+                 NFNL_MSG_TYPE(nlh->nlmsg_type));
+
+        /* Only requests are handled by kernel now. */
+        if (!(nlh->nlmsg_flags & NLM_F_REQUEST)) {
+                DEBUGP("received non-request message\n");
+                return 0;
+        }
+
+        /* All the messages must at least contain nfgenmsg */
+        if (nlh->nlmsg_len < 
+                        NLMSG_LENGTH(NLMSG_ALIGN(sizeof(struct nfgenmsg)))) {
+                DEBUGP("received message was too short\n");
+                return 0;
+        }
+
+        type = nlh->nlmsg_type;
+        ss = nfnetlink_get_subsys(type);
+        if (!ss)
+                goto err_inval;
+
+        nc = nfnetlink_find_client(type, ss);
+        if (!nc) {
+                DEBUGP("unable to find client for type %d\n", type);
+                goto err_inval;
+        }
+
+        if (nc->cap_required && 
+            !cap_raised(NETLINK_CB(skb).eff_cap, nc->cap_required)) {
+                DEBUGP("permission denied for type %d\n", type);
+                *errp = -EPERM;
+                return -1;
+        }
+
+        {
+                struct nfattr *cda[ss->attr_count];
+
+                memset(cda, 0, ss->attr_count*sizeof(struct nfattr *));
+                
+                err = nfnetlink_check_attributes(ss, nlh, cda);
+                if (err < 0)
+                        goto err_inval;
+
+                err = nc->call(nfnl, skb, nlh, cda, errp);
+                *errp = err;
+                return err;
+        }
+
+err_inval:
+        *errp = -EINVAL;
+        return -1;
+}
+
+/* Process one packet of messages. */
+static inline int nfnetlink_rcv_skb(struct sk_buff *skb)
+{
+        int err;
+        struct nlmsghdr *nlh;
+
+        while (skb->len >= NLMSG_SPACE(0)) {
+                u32 rlen;
+
+                nlh = (struct nlmsghdr *)skb->data;
+                if (nlh->nlmsg_len < sizeof(struct nlmsghdr)
+                    || skb->len < nlh->nlmsg_len)
+                        return 0;
+                rlen = NLMSG_ALIGN(nlh->nlmsg_len);
+                if (rlen > skb->len)
+                        rlen = skb->len;
+                if (nfnetlink_rcv_msg(skb, nlh, &err)) {
+                        if (!err)
+                                return -1;
+                        netlink_ack(skb, nlh, err);
+                } else
+                        if (nlh->nlmsg_flags & NLM_F_ACK)
+                                netlink_ack(skb, nlh, 0);
+                skb_pull(skb, rlen);
+        }
+
+        return 0;
+}
+
+static void nfnetlink_rcv(struct sock *sk, int len)
+{
+        do {
+                struct sk_buff *skb;
+
+                if (nfnl_shlock_nowait())
+                        return;
+
+                while ((skb = skb_dequeue(&sk->sk_receive_queue)) != NULL) {
+                        if (nfnetlink_rcv_skb(skb)) {
+                                if (skb->len)
+                                        skb_queue_head(&sk->sk_receive_queue,
+                                                       skb);
+                                else
+                                        kfree_skb(skb);
+                                break;
+                        }
+                        kfree_skb(skb);
+                }
+
+                up(&nfnl_sem);
+        } while(nfnl && nfnl->sk_receive_queue.qlen);
+}
+
+void __exit nfnetlink_exit(void)
+{
+        printk("Removing netfilter NETLINK layer.\n");
+        sock_release(nfnl->sk_socket);
+        return;
+}
+
+int __init nfnetlink_init(void)
+{
+        printk("Netfilter messages via NETLINK v%s.\n", nfversion);
+
+        nfnl = netlink_kernel_create(NETLINK_NETFILTER, nfnetlink_rcv);
+        if (!nfnl) {
+                printk(KERN_ERR "cannot initialize nfnetlink!\n");
+                return -1;
+        }
+
+        return 0;
+}
+
+module_init(nfnetlink_init);
+module_exit(nfnetlink_exit);
+
+EXPORT_SYMBOL_GPL(nfnetlink_subsys_register);
+EXPORT_SYMBOL_GPL(nfnetlink_subsys_unregister);
+EXPORT_SYMBOL_GPL(nfnetlink_send);
+EXPORT_SYMBOL_GPL(nfnetlink_unicast);
+EXPORT_SYMBOL_GPL(nfattr_parse);
+EXPORT_SYMBOL_GPL(__nfa_fill);