update ebpf c for inter

ubuntu_intermediate/inter_op_ebpf.c

+#include <linux/bpf.h>
+#include <linux/if_ether.h>
+#include <linux/ip.h>
+#include <linux/udp.h>
+
+#define MY_OPTION_TYPE 31 // Custom option type
+#define MAX_CHECKING 4
+
+static inline __u16 iph_csum(struct iphdr *iph, void *data_end)
+{
+    __u32 sum = 0;
+    __u16 *buf = (__u16 *)iph;
+    __u16 ihl = iph->ihl << 2; // Convert IHL to bytes
+
+    // Reset checksum field
+    iph->check = 0;
+
+    // Sum all 16-bit words in the header - 60 bytes is maximum size of IP header
+    for (__u8 i = 0; i < ihl && i < 60; i += 2)
+    {
+        if ((void *)(buf + 1) > data_end)
+        {
+            break;
+        }
+        sum += *buf++;
+    }
+
+    // Add overflow (carry folding)
+    for (__u8 i = 0; sum >> 16 && i < MAX_CHECKING; i += 1)
+    {
+        sum = (sum & 0xFFFF) + (sum >> 16);
+    }
+
+    // Take one's complement
+    return ~sum;
+}
+
+// CustomIPOption structure
+struct CustomIPEntry
+{
+    __u16 id_val;
+    __u8 inter_val;
+    __u8 cmd_val;
+} __attribute__((packed)); // Ensure packed struct to prevent padding issues
+
+int inter_op_ebpf(struct xdp_md *ctx)
+{
+    void *data = (void *)(long)ctx->data;
+    void *data_end = (void *)(long)ctx->data_end;
+
+    struct ethhdr *eth = data;
+
+    // Check if the Ethernet header is within bounds
+    if ((void *)eth + sizeof(*eth) > data_end)
+        return XDP_PASS;
+
+    struct iphdr *ip = data + sizeof(*eth);
+
+    // Check if the IP header is within bounds
+    if ((void *)ip + sizeof(*ip) > data_end)
+        return XDP_PASS;
+
+    if (ip->version != 4)
+    {
+        return XDP_PASS;
+    }
+
+    // Check if the packet has IP options
+    int options_len = (ip->ihl * 4) - sizeof(struct iphdr);
+    __u8 *options = (__u8 *)(ip + 1);
+
+    bpf_trace_printk("Packet received on interface %d and and ihl %d option length %d\n", ctx->ingress_ifindex, ip->ihl, options_len);
+
+    __u8 is_register = 1;
+    __u8 is_exist_custom_option = 0;
+    if (options_len > 0 && (void *)(options + 4) < data_end)
+    { // Ensure you're within the bounds (type + length + count = 4 bytes)
+        __u8 option_type = options[0];
+        if (option_type == MY_OPTION_TYPE)
+        {
+            is_exist_custom_option = 1;
+            __u8 option_length = options[1];
+
+            __u8 *data_bytes = (__u8 *)data;
+            int shift_data_length = sizeof(*eth) + sizeof(struct iphdr);
+
+            if (option_length == 8){
+                for (int i = shift_data_length - 1; i >= 0; i--) {
+                    if ((void *)(data_bytes + i + option_length + 1) > data_end)
+                        return XDP_PASS;
+
+                    data_bytes[i + option_length] = data_bytes[i];
+                }
+            }
+            else if (option_length == 12){
+                for (int i = shift_data_length - 1; i >= 0; i--) {
+                    if ((void *)(data_bytes + i + option_length + 1) > data_end)
+                        return XDP_PASS;
+
+                    data_bytes[i + option_length] = data_bytes[i];
+                }
+            }
+            else if (option_length == 16){
+                for (int i = shift_data_length - 1; i >= 0; i--) {
+                    if ((void *)(data_bytes + i + option_length + 1) > data_end)
+                        return XDP_PASS;
+
+                    data_bytes[i + option_length] = data_bytes[i];
+                }
+            }
+            else if (option_length == 20){
+                for (int i = shift_data_length - 1; i >= 0; i--) {
+                    if ((void *)(data_bytes + i + option_length + 1) > data_end)
+                        return XDP_PASS;
+
+                    data_bytes[i + option_length] = data_bytes[i];
+                }
+            }
+            else if (option_length == 24){
+                for (int i = shift_data_length - 1; i >= 0; i--) {
+                    if ((void *)(data_bytes + i + option_length + 1) > data_end)
+                        return XDP_PASS;
+
+                    data_bytes[i + option_length] = data_bytes[i];
+                }
+            }
+            else if (option_length == 28){
+                for (int i = shift_data_length - 1; i >= 0; i--) {
+                    if ((void *)(data_bytes + i + option_length + 1) > data_end)
+                        return XDP_PASS;
+
+                    data_bytes[i + option_length] = data_bytes[i];
+                }
+            }
+            else if (option_length == 32){
+                for (int i = shift_data_length - 1; i >= 0; i--) {
+                    if ((void *)(data_bytes + i + option_length + 1) > data_end)
+                        return XDP_PASS;
+
+                    data_bytes[i + option_length] = data_bytes[i];
+                }
+            }
+     
+
+            int ret = bpf_xdp_adjust_head(ctx, option_length); // Cut option length bytes at the head
+            if (ret < 0)
+            {
+                return XDP_PASS; // If adjustment fails, pass the packet
+            }
+
+            data = (void *)(long)ctx->data;
+            data_end = (void *)(long)ctx->data_end;
+        
+            eth = data;
+        
+            // Check if the Ethernet header is within bounds
+            if ((void *)eth + sizeof(*eth) > data_end)
+                return XDP_DROP;
+        
+            ip = data + sizeof(*eth);
+        
+            // Check if the IP header is within bounds
+            if ((void *)ip + sizeof(*ip) > data_end)
+                return XDP_DROP;
+        
+            if (ip->version != 4)
+            {
+                return XDP_DROP;
+            }
+
+            int new_header_size = sizeof(struct iphdr); // 20 + 8 = 28 bytes
+            ip->ihl = new_header_size / 4;
+            ip->tot_len = htons(ntohs(ip->tot_len) - option_length);
+
+            // bpf_trace_printk("Packet received on interface %d and option length %d\n", ctx->ingress_ifindex, options_len);
+            // ip->check = iph_csum(ip, data_end);
+        }
+    }
+
+    ip->check = iph_csum(ip, data_end);
+
+    return XDP_PASS;
+}