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Subject[PATCH] 2.4.8 frame diverter for modules
Here is a patch against 2.4.8 that implements support for diverting network frames
to an arbitrary kernel module. It is similar to the user-level packet diverter
except that it handles both incoming and outgoing packets, and the module can
discard the packet if it wants to. There is also a callback when a packet is freed.
This allows a modular way of doing low-level packet frobbing without going out to
userland.

As noted in the code, it currently only supports 1 'diverter module', but it would
be pretty easy to support more...

Comments? Anyone find this sort of thing useful besides us?

--
-Will :: AD6XL :: http://www.loopfree.net/
Orton :: finger will@tyranny.egregious.net for GPG public key
diff -urP linux-clean/include/linux/moddv.h linux/include/linux/moddv.h
--- linux-clean/include/linux/moddv.h Wed Dec 31 16:00:00 1969
+++ linux/include/linux/moddv.h Thu Aug 16 11:50:10 2001
@@ -0,0 +1,31 @@
+#ifndef _MODDV_H_
+#define _MODDV_H_
+
+struct moddv_calls {
+ atomic_t unloading;
+ atomic_t usage;
+ int (*divert_tx)(struct sk_buff **, struct net_device **, struct packet_type **);
+ int (*divert_rx)(struct sk_buff **, struct net_device **, struct packet_type **);
+ void (*divert_bind)(struct net_device *, struct packet_type *);
+ void (*divert_free)(struct sk_buff *);
+};
+
+extern int register_divert_module(struct moddv_calls *);
+extern void unregister_divert_module( struct moddv_calls * );
+void mod_divert_inject_out( struct sk_buff *, struct net_device *);
+void mod_divert_inject_in( struct sk_buff *, struct net_device *, struct packet_type *);
+
+int handle_mod_divert_tx(struct sk_buff **, struct net_device **);
+int handle_mod_divert_rx(struct sk_buff **, struct net_device **, struct packet_type **);
+void mod_divert_skb_use(struct sk_buff *);
+void mod_divert_skb_unuse(struct sk_buff *);
+void mod_divert_init(void);
+
+extern struct moddv_calls *diverter;
+
+#define MDV_DISCARD 1
+#define MDV_HOLD 2
+#define MDV_CHAIN 3
+
+
+#endif /* _MODDV_H_ */
diff -urP linux-clean/include/linux/netdevice.h linux/include/linux/netdevice.h
--- linux-clean/include/linux/netdevice.h Thu Aug 16 12:43:55 2001
+++ linux/include/linux/netdevice.h Thu Aug 16 16:07:35 2001
@@ -418,6 +418,9 @@
struct packet_type *);
void *data; /* Private to the packet type */
struct packet_type *next;
+#ifdef CONFIG_MOD_DIVERT
+ void *divertPtr; /* Private ptr for the module diverter */
+#endif
};


diff -urP linux-clean/include/linux/skbuff.h linux/include/linux/skbuff.h
--- linux-clean/include/linux/skbuff.h Thu Aug 16 12:43:55 2001
+++ linux/include/linux/skbuff.h Thu Aug 16 11:53:34 2001
@@ -213,6 +213,9 @@
#ifdef CONFIG_NET_SCHED
__u32 tc_index; /* traffic control index */
#endif
+#ifdef CONFIG_MOD_DIVERT
+ void *divertPtr1;
+#endif
};

#define SK_WMEM_MAX 65535
diff -urP linux-clean/net/Config.in linux/net/Config.in
--- linux-clean/net/Config.in Thu Aug 16 12:44:11 2001
+++ linux/net/Config.in Thu Aug 16 11:58:34 2001
@@ -64,6 +64,7 @@
tristate 'LAPB Data Link Driver (EXPERIMENTAL)' CONFIG_LAPB
bool '802.2 LLC (EXPERIMENTAL)' CONFIG_LLC
bool 'Frame Diverter (EXPERIMENTAL)' CONFIG_NET_DIVERT
+ bool 'Frame diverter for modules (EXPERIMENTAL)' CONFIG_MOD_DIVERT
# if [ "$CONFIG_LLC" = "y" ]; then
# bool ' Netbeui (EXPERIMENTAL)' CONFIG_NETBEUI
# fi
diff -urP linux-clean/net/core/Makefile linux/net/core/Makefile
--- linux-clean/net/core/Makefile Thu Aug 16 12:44:10 2001
+++ linux/net/core/Makefile Thu Aug 16 12:14:53 2001
@@ -24,6 +24,7 @@
obj-$(CONFIG_NET) += dev.o dev_mcast.o dst.o neighbour.o rtnetlink.o utils.o

obj-$(CONFIG_NETFILTER) += netfilter.o
+obj-$(CONFIG_MOD_DIVERT) += moddv.o
obj-$(CONFIG_NET_DIVERT) += dv.o
obj-$(CONFIG_NET_PROFILE) += profile.o

diff -urP linux-clean/net/core/dev.c linux/net/core/dev.c
--- linux-clean/net/core/dev.c Thu Aug 16 12:44:10 2001
+++ linux/net/core/dev.c Thu Aug 16 12:09:11 2001
@@ -103,6 +103,9 @@
#if defined(CONFIG_NET_RADIO) || defined(CONFIG_NET_PCMCIA_RADIO)
#include <linux/wireless.h> /* Note : will define WIRELESS_EXT */
#endif /* CONFIG_NET_RADIO || CONFIG_NET_PCMCIA_RADIO */
+#ifdef CONFIG_MOD_DIVERT
+#include <linux/moddv.h>
+#endif /* CONFIG_MOD_DIVERT */
#ifdef CONFIG_PLIP
extern int plip_init(void);
#endif
@@ -152,8 +155,13 @@
* 86DD IPv6
*/

+#ifdef CONFIG_MOD_DIVERT
+struct packet_type *ptype_base[16]; /* 16 way hashed list */
+struct packet_type *ptype_all = NULL; /* Taps */
+#else /* !CONFIG_MOD_DIVERT */
static struct packet_type *ptype_base[16]; /* 16 way hashed list */
static struct packet_type *ptype_all = NULL; /* Taps */
+#endif /* !CONFIG_MOD_DIVERT */

#ifdef OFFLINE_SAMPLE
static void sample_queue(unsigned long dummy);
@@ -987,6 +995,12 @@
return -ENOMEM;
}

+ /* call the module diverter */
+#ifdef CONFIG_MOD_DIVERT
+ if (handle_mod_divert_tx(&skb, &dev))
+ return NET_XMIT_SUCCESS;
+#endif
+
/* Grab device queue */
spin_lock_bh(&dev->queue_lock);
q = dev->qdisc;
@@ -1475,6 +1489,10 @@
deliver_to_old_ones(pt_prev, skb, 0);
else {
atomic_inc(&skb->users);
+#ifdef CONFIG_MOD_DIVERT
+ if (handle_mod_divert_rx(&skb, &rx_dev, &pt_prev))
+ goto DEAD_PACKET;
+#endif /* CONFIG_MOD_DIVERT */
pt_prev->func(skb,
skb->dev,
pt_prev);
@@ -1487,12 +1505,19 @@
if (pt_prev) {
if (!pt_prev->data)
deliver_to_old_ones(pt_prev, skb, 1);
- else
+ else {
+#ifdef CONFIG_MOD_DIVERT
+ if (handle_mod_divert_rx(&skb, &rx_dev, &pt_prev))
+ goto DEAD_PACKET;
+#endif /* CONFIG_MOD_DIVERT */
pt_prev->func(skb, skb->dev, pt_prev);
+ }
} else
kfree_skb(skb);
}
-
+#ifdef CONFIG_MOD_DIVERT
+DEAD_PACKET:
+#endif
dev_put(rx_dev);

if (bugdet-- < 0 || jiffies - start_time > 1)
@@ -2783,7 +2808,10 @@
*/

net_device_init();
-
+
+#ifdef CONFIG_MOD_DIVERT
+ mod_divert_init();
+#endif /* CONFIG_MOD_DIVERT */
return 0;
}

diff -urP linux-clean/net/core/moddv.c linux/net/core/moddv.c
--- linux-clean/net/core/moddv.c Wed Dec 31 16:00:00 1969
+++ linux/net/core/moddv.c Thu Aug 16 11:50:10 2001
@@ -0,0 +1,239 @@
+/*
+ * Module level frame diverter.
+ *
+ * File: moddv.c
+ *
+ * Purpose: This file in conjunction with the #ifdef CONFIG_MOD_DIVERT section inside
+ * of dev.c, skbuff.c, skbuff.h and netdevice.h form a full packet diverter for modules.
+ * This system is similar to the user level packet diverter, except it also gets
+ * outgoing packets, and may discard both incomming and outgoing packet. There is
+ * also a callback for packets being freed.
+ *
+ * Currently only one diverter module is allowed to register. This could be changed
+ * in the furture to accomodate a priority based list such as is used in netfilter.
+ *
+ * Currently this implementation is for kernel modules only. Anyone wanting an ioctl
+ * interface, feel free to write one...
+ *
+ * Authors: Seth Keith ( seth@deterministicnetworks.com )
+ * Will Orton ( worton@deterministicnetworks.com )
+ */
+
+#include <asm/uaccess.h>
+#include <asm/system.h>
+#include <asm/bitops.h>
+#include <linux/config.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/string.h>
+#include <linux/mm.h>
+#include <linux/socket.h>
+#include <linux/sockios.h>
+#include <linux/errno.h>
+#include <linux/interrupt.h>
+#include <linux/if_ether.h>
+#include <linux/netdevice.h>
+#include <linux/etherdevice.h>
+#include <linux/notifier.h>
+#include <linux/skbuff.h>
+#include <linux/brlock.h>
+#include <net/sock.h>
+#include <linux/rtnetlink.h>
+#include <linux/proc_fs.h>
+#include <linux/stat.h>
+#include <linux/if_bridge.h>
+#include <linux/divert.h>
+#include <net/dst.h>
+#include <net/pkt_sched.h>
+#include <net/profile.h>
+#include <net/checksum.h>
+#include <linux/highmem.h>
+#include <linux/init.h>
+#include <linux/kmod.h>
+#include <linux/module.h>
+#include <linux/moddv.h>
+
+spinlock_t divertLock;
+struct moddv_calls *diverter = NULL;
+static int initted = 0;
+
+extern struct packet_type *ptype_base[16];
+extern struct packet_type *ptype_all;
+extern int dev_queue_xmit( struct sk_buff *);
+
+__inline int enter_diverter(void)
+{
+ if (!initted)
+ return 1;
+
+ spin_lock_bh(&divertLock);
+ if (!diverter || atomic_read(&(diverter->unloading))) {
+ spin_unlock_bh(&divertLock);
+ return 1;
+ } else {
+ spin_unlock_bh(&divertLock);
+ atomic_inc(&diverter->usage);
+ return 0;
+ }
+}
+
+__inline void exit_diverter(void)
+{
+ spin_lock_bh(&divertLock);
+ if (!diverter) {
+ spin_unlock_bh(&divertLock);
+ } else {
+ atomic_dec(&diverter->usage);
+ spin_unlock_bh(&divertLock);
+ }
+}
+
+void __init mod_divert_init(void)
+{
+ spin_lock_init(&divertLock);
+ initted = 1;
+}
+
+void call_bind(void)
+{
+ struct net_device *dev;
+ struct packet_type *pt;
+ int i;
+
+ for (dev = dev_base; dev != NULL; dev = dev->next) {
+ for (i = 0; i < 16; i++) {
+ for (pt = ptype_base[i]; pt != NULL; pt = pt->next) {
+ if (diverter->divert_bind)
+ diverter->divert_bind(dev, pt);
+ }
+ }
+ }
+}
+
+int register_divert_module(struct moddv_calls *regcalls)
+{
+ /* Right now we just handle one. This can easily be changed.
+ */
+ spin_lock_bh(&divertLock);
+
+ if (diverter) {
+ printk(KERN_ERR "Only one diverter is currently supported, and one is already registered.\n");
+ spin_unlock_bh(&divertLock);
+ return 1;
+ }
+
+ diverter = regcalls;
+ spin_unlock_bh(&divertLock);
+ call_bind();
+ return 0;
+}
+
+void unregister_divert_module(struct moddv_calls *regcalls)
+{
+ atomic_set(&diverter->unloading, 1);
+ while (atomic_read(&diverter->usage))
+ schedule();
+
+ spin_lock_bh(&divertLock);
+ diverter = NULL;
+ spin_unlock_bh(&divertLock);
+}
+
+int handle_mod_divert_tx(struct sk_buff **skb, struct net_device **dev)
+{
+ struct packet_type *proto = NULL;
+
+ if (enter_diverter() || !diverter->divert_tx)
+ return 0;
+
+ if ((*skb)->divertPtr1 != NULL) {
+ exit_diverter();
+ return 0;
+ }
+
+ for (proto = ptype_base[ntohs((*skb)->protocol) & 15]; proto; proto = proto->next) {
+ if (proto->type == (*skb)->protocol && (!proto->dev || proto->dev == (*skb)->dev)) {
+ break;
+ }
+ }
+
+ if (!proto) {
+ printk(KERN_ERR "Diverting a packet to a module but cannot find the correct protocol?");
+ exit_diverter();
+ return 0;
+ }
+
+ switch (diverter->divert_tx(skb, dev, &proto)) {
+ case MDV_DISCARD:
+ kfree_skb(*skb);
+ exit_diverter();
+ return 1;
+ case MDV_HOLD:
+ exit_diverter();
+ return 1;
+ case MDV_CHAIN:
+ exit_diverter();
+ return 0;
+ default:
+ printk(KERN_ERR "Diverter module return an invalid return code from TX!\n");
+ exit_diverter();
+ return 1;
+ }
+}
+
+int handle_mod_divert_rx(struct sk_buff **skb, struct net_device **dev, struct packet_type **proto )
+{
+ if (enter_diverter() || !diverter->divert_rx)
+ return 0;
+
+ if ((*skb)->divertPtr1 != NULL) {
+ exit_diverter();
+ return 0;
+ }
+
+ switch (diverter->divert_rx(skb, dev, proto)) {
+ case MDV_DISCARD:
+ kfree_skb(*skb);
+ exit_diverter();
+ return 1;
+ case MDV_HOLD:
+ exit_diverter();
+ return 1;
+ case MDV_CHAIN:
+ exit_diverter();
+ return 0;
+ default:
+ printk(KERN_ERR "Diverter module return an invalid return code from RX!\n");
+ exit_diverter();
+ return 1;
+ }
+}
+
+void mod_divert_skb_use(struct sk_buff *skb)
+{
+ enter_diverter();
+ exit_diverter();
+}
+
+void mod_divert_skb_unuse(struct sk_buff *skb)
+{
+ if (skb->divertPtr1) {
+ enter_diverter();
+ if (diverter->divert_free)
+ diverter->divert_free(skb);
+ exit_diverter();
+ }
+}
+
+void mod_divert_inject_out(struct sk_buff *skb, struct net_device *dev)
+{
+ skb->dev = dev;
+ dev_queue_xmit(skb);
+}
+
+void mod_divert_inject_in(struct sk_buff *skb, struct net_device *dev, struct packet_type *proto)
+{
+ skb->dev = dev;
+ proto->func(skb, dev, proto);
+}
diff -urP linux-clean/net/core/skbuff.c linux/net/core/skbuff.c
--- linux-clean/net/core/skbuff.c Thu Aug 16 12:44:10 2001
+++ linux/net/core/skbuff.c Thu Aug 16 12:35:20 2001
@@ -51,6 +51,9 @@
#include <linux/cache.h>
#include <linux/init.h>
#include <linux/highmem.h>
+#ifdef CONFIG_MOD_DIVERT
+#include <linux/moddv.h>
+#endif /* CONFIG_MOD_DIVERT */

#include <net/ip.h>
#include <net/protocol.h>
@@ -209,6 +212,9 @@
atomic_set(&(skb_shinfo(skb)->dataref), 1);
skb_shinfo(skb)->nr_frags = 0;
skb_shinfo(skb)->frag_list = NULL;
+#ifdef CONFIG_MOD_DIVERT
+ skb->divertPtr1 = NULL;
+#endif
return skb;

nodata:
@@ -250,6 +256,9 @@
#ifdef CONFIG_NET_SCHED
skb->tc_index = 0;
#endif
+#ifdef CONFIG_MOD_DIVERT
+ skb->divertPtr1 = NULL;
+#endif /* CONFIG_MOD_DIVERT */
}

static void skb_drop_fraglist(struct sk_buff *skb)
@@ -275,6 +284,9 @@

static void skb_release_data(struct sk_buff *skb)
{
+#ifdef CONFIG_MOD_DIVERT
+ if (skb->head) {
+#endif
if (!skb->cloned ||
atomic_dec_and_test(&(skb_shinfo(skb)->dataref))) {
if (skb_shinfo(skb)->nr_frags) {
@@ -288,6 +300,9 @@

kfree(skb->head);
}
+#ifdef CONFIG_MOD_DIVERT
+ }
+#endif
}

/*
@@ -316,7 +331,12 @@
BUG();
}

+#ifdef CONFIG_MOD_DIVERT
+ if (skb->dst)
+ dst_release(skb->dst);
+#else
dst_release(skb->dst);
+#endif
if(skb->destructor) {
if (in_irq()) {
printk(KERN_WARNING "Warning: kfree_skb on hard IRQ %p\n",
@@ -327,6 +347,10 @@
#ifdef CONFIG_NETFILTER
nf_conntrack_put(skb->nfct);
#endif
+#ifdef CONFIG_MOD_DIVERT
+ if (skb->divertPtr1)
+ mod_divert_skb_unuse(skb);
+#endif /* CONFIG_MOD_DIVERT */
skb_headerinit(skb, NULL, 0); /* clean state */
kfree_skbmem(skb);
}
@@ -404,6 +428,9 @@
skb->cloned = 1;
#ifdef CONFIG_NETFILTER
nf_conntrack_get(skb->nfct);
+#endif
+#ifdef CONFIG_MOD_DIVERT
+ n->divertPtr1 = NULL;
#endif
return n;
}
diff -urP linux-clean/net/netsyms.c linux/net/netsyms.c
--- linux-clean/net/netsyms.c Thu Aug 16 12:44:09 2001
+++ linux/net/netsyms.c Thu Aug 16 12:00:38 2001
@@ -34,6 +34,9 @@
#ifdef CONFIG_NET_DIVERT
#include <linux/divert.h>
#endif /* CONFIG_NET_DIVERT */
+#ifdef CONFIG_MOD_DIVERT
+#include <linux/moddv.h>
+#endif /* CONFIG_MOD_DIVERT */

#ifdef CONFIG_NET
extern __u32 sysctl_wmem_max;
@@ -230,6 +233,11 @@
EXPORT_SYMBOL(free_divert_blk);
EXPORT_SYMBOL(divert_ioctl);
#endif /* CONFIG_NET_DIVERT */
+
+#ifdef CONFIG_MOD_DIVERT
+EXPORT_SYMBOL_NOVERS(register_divert_module);
+EXPORT_SYMBOL_NOVERS(unregister_divert_module);
+#endif /* CONFIG_MOD_DIVERT */

#ifdef CONFIG_INET
/* Internet layer registration */
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