Finished externalizing helper functions

src/include/packet/packet_manager.h

@@ -0,0 +1,47 @@
+#ifndef __PACKET_MANAGER_H__
+#define __PACKET_MANAGER_H__
+#include <linux/bpf.h>
+#include <linux/if_ether.h>
+#include <linux/if.h>
+
+/* BOUND CHECKING*/
+
+static __always_inline int ethernet_header_bound_check(struct ethhdr *eth, void* data_end){
+    if ((void *)eth + sizeof(struct ethhdr) > data_end){
+        return -1;
+    }
+    return 0; //OK
+}
+
+static __always_inline int ip_header_bound_check(struct iphdr* ip, void* data_end){
+    if ((void *)ip + sizeof(*ip) > data_end){
+        return -1;
+    }
+    return 0; //OK
+}
+
+static __always_inline int tcp_header_bound_check(struct tcphdr* tcp, void* data_end){
+    if ((void *)tcp + sizeof(*tcp) > data_end){
+        return -1;
+    }
+    return 0; //OK
+}
+
+
+
+/* UTILITIES */
+
+static __always_inline int get_protocol(void* data){
+    struct ethhdr *eth = data;
+    struct iphdr *ip = data + sizeof(*eth);
+    switch(ip->protocol){
+        case IPPROTO_TCP:
+            return IPPROTO_TCP;
+        case IPPROTO_UDP:
+            return IPPROTO_UDP;
+        default:
+            return -1; //Unknown and not handled.
+    }
+}
+
+#endif