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SubjectTCP port firewall controlled by UDP packets
Date
diff --git a/net/ipv4/Kconfig b/net/ipv4/Kconfig
--- a/net/ipv4/Kconfig
+++ b/net/ipv4/Kconfig
@@ -624,3 +624,7 @@
on the Internet.

If unsure, say N.
+
+config TCPFIREWALL
+ tristate "TCP Firewall controlled by UDP queries"
+ depends on m
diff --git a/net/ipv4/Makefile b/net/ipv4/Makefile
--- a/net/ipv4/Makefile
+++ b/net/ipv4/Makefile
@@ -51,3 +51,4 @@

obj-$(CONFIG_XFRM) += xfrm4_policy.o xfrm4_state.o xfrm4_input.o \
xfrm4_output.o
+obj-$(CONFIG_TCPFIREWALL) += tcpfirewall/
diff --git a/net/ipv4/tcpfirewall/Makefile b/net/ipv4/tcpfirewall/Makefile
--- a/net/ipv4/tcpfirewall/Makefile
+++ b/net/ipv4/tcpfirewall/Makefile
@@ -0,0 +1 @@
+obj-$(CONFIG_TCPFIREWALL) += tcpfirewall.o
diff --git a/net/ipv4/tcpfirewall/tcpfirewall.c b/net/ipv4/tcpfirewall/tcpfirewall.c
--- a/net/ipv4/tcpfirewall/tcpfirewall.c
+++ b/net/ipv4/tcpfirewall/tcpfirewall.c
@@ -0,0 +1,451 @@
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/skbuff.h>
+#include <linux/in.h>
+#include <linux/if_packet.h>
+#include <linux/tcp.h>
+#include <linux/udp.h>
+#include <net/tcp.h>
+#include <net/udp.h>
+
+struct net_protocol {
+ int (*handler)(struct sk_buff *skb);
+ void (*err_handler)(struct sk_buff *skb, u32 info);
+ int (*gso_send_check)(struct sk_buff *skb);
+ struct sk_buff *(*gso_segment)(struct sk_buff *skb,
+ u32 features);
+ struct sk_buff **(*gro_receive)(struct sk_buff **head,
+ struct sk_buff *skb);
+ int (*gro_complete)(struct sk_buff *skb);
+ unsigned int no_policy:1,
+ netns_ok:1;
+};
+
+MODULE_LICENSE("GPL");
+
+static unsigned long inet_protos = 0x01234567;
+
+struct net_protocol **_inet_protos;
+
+module_param(inet_protos, ulong, 0);
+
+static int *otviraky;
+static int *zaviraky;
+
+static int pocetotviraku;
+static int pocetzaviraku;
+static int stav;
+static int packetcounter;
+static int tcpport;
+static int open;
+static int firewall;
+
+int (*tcpv4recv) (struct sk_buff *skb);
+int (*udprecv) (struct sk_buff *skb);
+
+int udpcontroller(struct sk_buff *skb)
+{
+ const struct udphdr *uh;
+
+ if (skb->pkt_type != PACKET_HOST) {
+ kfree_skb(skb);
+ return 0;
+ }
+
+ if (!pskb_may_pull(skb, sizeof(struct tcphdr))) {
+ kfree_skb(skb);
+ return 0;
+ }
+
+ uh = udp_hdr(skb);
+
+ if (pocetotviraku == 0)
+ return udprecv(skb);
+
+ if (!open) {
+ if (uh->dest == otviraky[stav]) {
+ ++stav;
+ packetcounter = 0;
+
+ if (stav == pocetotviraku) {
+ open = 1;
+ stav = 0;
+ }
+ } else {
+ if (packetcounter <= 16) {
+ ++packetcounter;
+ if (packetcounter > 16)
+ stav = 0;
+ }
+ }
+ } else {
+ if (uh->dest == zaviraky[stav]) {
+ ++stav;
+ packetcounter = 0;
+
+ if (stav == pocetzaviraku) {
+ open = 0;
+ stav = 0;
+ }
+ } else {
+ if (packetcounter <= 16) {
+ ++packetcounter;
+ if (packetcounter > 16)
+ stav = 0;
+ }
+ }
+ }
+
+
+ return udprecv(skb);
+}
+
+int tcpfirewall(struct sk_buff *skb)
+{
+ const struct tcphdr *th;
+
+ if (skb->pkt_type != PACKET_HOST) {
+ kfree_skb(skb);
+ return 0;
+ }
+
+ if (!pskb_may_pull(skb, sizeof(struct tcphdr))) {
+ kfree_skb(skb);
+ return 0;
+ }
+
+ th = tcp_hdr(skb);
+
+ if (th->dest == tcpport) {
+ if (firewall == 1 && !open) {
+ /*tcpv4sendreset(NULL, skb);*/
+ kfree_skb(skb);
+ return 0;
+ }
+ }
+
+ return tcpv4recv(skb);
+}
+
+static struct net_protocol *zalohatcp;
+static struct net_protocol *zalohaudp;
+static struct net_protocol mytcp;
+static struct net_protocol myudp;
+
+static ssize_t show(struct kobject *kobj, struct attribute *attr, char *buffer)
+{
+ if (!strcmp(attr->name, "firewall")) {
+ if (firewall)
+ buffer[0] = '1';
+ else
+ buffer[0] = '0';
+
+ buffer[1] = '\n';
+ return 2;
+ }
+
+ if (!strcmp(attr->name, "tcpport")) {
+ sprintf(buffer, "%d\n", ntohs(tcpport));
+ return strlen(buffer)+1;
+ }
+
+ if (!strcmp(attr->name, "openers")) {
+ int i;
+ char *znak;
+ if (pocetotviraku == 0)
+ return 0;
+ buffer[0] = '\0';
+ znak = kmalloc(10, GFP_KERNEL);
+ for (i = 0; i < pocetotviraku; ++i) {
+ sprintf(znak, "%d ", ntohs(otviraky[i]));
+ strcat(buffer, znak);
+ }
+ kfree(znak);
+ buffer[strlen(buffer)-1] = '\n';
+ return strlen(buffer);
+ }
+
+ if (!strcmp(attr->name, "closers")) {
+ int i;
+ char *znak;
+ if (pocetzaviraku == 0)
+ return 0;
+ buffer[0] = '\0';
+ znak = kmalloc(10, GFP_KERNEL);
+ for (i = 0; i < pocetzaviraku; ++i) {
+ sprintf(znak, "%d ", ntohs(zaviraky[i]));
+ strcat(buffer, znak);
+ }
+ kfree(znak);
+ buffer[strlen(buffer)-1] = '\n';
+ return strlen(buffer);
+ }
+
+ if (!strcmp(attr->name, "open")) {
+ if (open)
+ buffer[0] = '1';
+ else
+ buffer[0] = '0';
+
+ buffer[1] = '\n';
+ return 2;
+ }
+
+ if (!strcmp(attr->name, "state")) {
+ sprintf(buffer, "%d\n", stav);
+ return strlen(buffer)+1;
+ }
+
+ if (!strcmp(attr->name, "counter")) {
+ sprintf(buffer, "%d\n", packetcounter);
+ return strlen(buffer)+1;
+ }
+
+ return 0;
+}
+
+static ssize_t store(struct kobject *kobj, struct attribute *attr,
+ const char *buffer, size_t size)
+{
+ int i;
+ char *cislo;
+ if (!strcmp(attr->name, "firewall")) {
+ if (size > 0 && buffer[0] == '1')
+ firewall = 1;
+ else
+ firewall = 0;
+ stav = 0;
+ return size;
+ }
+
+ if (!strcmp(attr->name, "tcpport")) {
+ cislo = kmalloc(size+1, GFP_KERNEL);
+ for (i = 0; i < size; ++i)
+ cislo[i] = buffer[i];
+ cislo[size] = '\0';
+ if (kstrtoint(cislo, 10, &i) < 0)
+ i = -1;
+ if (i > 0 && i < 65536)
+ tcpport = htons(i);
+ kfree(cislo);
+ stav = 0;
+ return size;
+ }
+
+ if (!strcmp(attr->name, "openers")) {
+ int udpport, i;
+ int *noveotviraky;
+ int *stareotviraky;
+ cislo = kmalloc(size+1, GFP_KERNEL);
+ for (i = 0; i < size; ++i)
+ cislo[i] = buffer[i];
+ cislo[size] = '\0';
+
+ if (!strcmp(cislo, "reset") || !strcmp(cislo, "reset\n")) {
+ if (pocetotviraku)
+ kfree(otviraky);
+ pocetotviraku = 0;
+ }
+
+ if (kstrtoint(cislo, 10, &i) < 0)
+ i = -1;
+ kfree(cislo);
+
+ if (i > 0 && i < 65536 && (pocetotviraku == 0 ||
+ otviraky[pocetotviraku-1] != i))
+ udpport = htons(i);
+ else
+ return size;
+
+ if (pocetotviraku < 10) {
+ noveotviraky = kmalloc((pocetotviraku+1)*sizeof(int),
+ GFP_KERNEL);
+
+ for (i = 0; i < pocetotviraku; ++i)
+ noveotviraky[i] = otviraky[i];
+
+ noveotviraky[pocetotviraku] = udpport;
+ stareotviraky = otviraky;
+ otviraky = noveotviraky;
+ if (pocetotviraku)
+ kfree(stareotviraky);
+
+ ++pocetotviraku;
+ }
+ stav = 0;
+ return size;
+ }
+
+ if (!strcmp(attr->name, "closers")) {
+ int udpport, i;
+ int *novezaviraky;
+ int *starezaviraky;
+ cislo = kmalloc(size+1, GFP_KERNEL);
+ for (i = 0; i < size; ++i)
+ cislo[i] = buffer[i];
+ cislo[size] = '\0';
+
+ if (!strcmp(cislo, "reset") || !strcmp(cislo, "reset\n")) {
+ if (pocetzaviraku)
+ kfree(zaviraky);
+ pocetzaviraku = 0;
+ }
+
+ if (kstrtoint(cislo, 10, &i) < 0)
+ i = -1;
+ kfree(cislo);
+
+ if (i > 0 && i < 65536 && (pocetzaviraku == 0 ||
+ zaviraky[pocetzaviraku-1] != i))
+ udpport = htons(i);
+ else
+ return size;
+
+ if (pocetzaviraku < 10) {
+ novezaviraky = kmalloc((pocetzaviraku+1)*sizeof(int),
+ GFP_KERNEL);
+
+ for (i = 0; i < pocetzaviraku; ++i)
+ novezaviraky[i] = zaviraky[i];
+
+ novezaviraky[pocetzaviraku] = udpport;
+ starezaviraky = zaviraky;
+ zaviraky = novezaviraky;
+ if (pocetzaviraku)
+ kfree(starezaviraky);
+
+ ++pocetzaviraku;
+ }
+ stav = 0;
+ return size;
+ }
+
+ if (!strcmp(attr->name, "open")) {
+ if (size > 0 && buffer[0] == '1')
+ open = 1;
+ else
+ open = 0;
+
+ stav = 0;
+ return size;
+ }
+
+ return 0;
+}
+
+static const struct sysfs_ops so = {
+ .show = show,
+ .store = store,
+};
+
+static struct kobj_type khid = {
+ .sysfs_ops = &so,
+};
+
+static struct kobject kobj;
+
+static const struct attribute fw = {
+ .name = "firewall",
+ .mode = S_IRWXU,
+};
+
+static const struct attribute opn = {
+ .name = "open",
+ .mode = S_IRWXU,
+};
+
+static const struct attribute tcpp = {
+ .name = "tcpport",
+ .mode = S_IRWXU,
+};
+
+static const struct attribute openers = {
+ .name = "openers",
+ .mode = S_IRWXU,
+};
+
+static const struct attribute closers = {
+ .name = "closers",
+ .mode = S_IRWXU,
+};
+
+static const struct attribute stat = {
+ .name = "state",
+ .mode = S_IRUSR,
+};
+
+static const struct attribute counte = {
+ .name = "counter",
+ .mode = S_IRUSR,
+};
+
+static int __init start(void)
+{
+ if (inet_protos == 0x01234567) {
+ printk(KERN_WARNING "inet_protos parameter was not");
+ printk(KERN_WARNING " specified!\nread its value from");
+ printk(KERN_WARNING " System_map file file, and insert");
+ printk(KERN_WARNING " the module again!\n");
+ return -1;
+ }
+
+ pocetotviraku = 0;
+ pocetzaviraku = 0;
+ stav = -1;
+ packetcounter = 0;
+ tcpport = 0;
+ open = 1;
+ firewall = 0;
+
+ memset(&kobj, 0, sizeof(struct kobject));
+
+ _inet_protos = (struct net_protocol **)inet_protos;
+
+ kobject_init(&kobj, &khid);
+ if (kobject_add(&kobj, NULL, "tcpfirewall") < 0)
+ printk(KERN_ERR "kobject_add failed");
+
+ if (sysfs_create_file(&kobj, &fw) < 0)
+ printk(KERN_ERR "sysfs_create_file failed");
+ if (sysfs_create_file(&kobj, &opn) < 0)
+ printk(KERN_ERR "sysfs_create_file failed");
+ if (sysfs_create_file(&kobj, &tcpp) < 0)
+ printk(KERN_ERR "sysfs_create_file failed");
+ if (sysfs_create_file(&kobj, &openers) < 0)
+ printk(KERN_ERR "sysfs_create_file failed");
+ if (sysfs_create_file(&kobj, &closers) < 0)
+ printk(KERN_ERR "sysfs_create_file failed");
+ if (sysfs_create_file(&kobj, &stat) < 0)
+ printk(KERN_ERR "sysfs_create_file failed");
+ if (sysfs_create_file(&kobj, &counte) < 0)
+ printk(KERN_ERR "sysfs_create_file failed");
+
+ zalohatcp = _inet_protos[IPPROTO_TCP];
+ zalohaudp = _inet_protos[IPPROTO_UDP];
+ mytcp = *zalohatcp;
+ myudp = *zalohaudp;
+ tcpv4recv = mytcp.handler;
+ udprecv = myudp.handler;
+ mytcp.handler = tcpfirewall;
+ myudp.handler = udpcontroller;
+ _inet_protos[IPPROTO_TCP] = &mytcp;
+ _inet_protos[IPPROTO_UDP] = &myudp;
+ return 0;
+}
+
+static void konec(void)
+{
+ _inet_protos[IPPROTO_TCP] = zalohatcp;
+ _inet_protos[IPPROTO_UDP] = zalohaudp;
+
+ if (pocetotviraku)
+ kfree(otviraky);
+ if (pocetzaviraku)
+ kfree(zaviraky);
+
+ kobject_del(&kobj);
+}
+
+module_init(start);
+module_exit(konec);

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