udp.p4

/**
 * UDP Header Definition in P4
 * User Datagram Protocol for connectionless communication
 * 
 * Note: UDP provides minimal transport layer services with no reliability guarantees,
 *       commonly used for real-time and low-latency applications
 */

/* Well-known UDP Ports */
enum bit<8> udp_ports {
    DNS = 53,          // Domain Name System
    DHCP_CLIENT = 68,  // DHCP Client
    DHCP_SERVER = 67,  // DHCP Server
    NTP = 123,         // Network Time Protocol
    SNMP = 161,        // Simple Network Management
    TFTP = 69          // Trivial File Transfer
};

/**
 * UDP Header (8 bytes)
 * Standard UDP header format
 */
header udp_header {
    bit<16> src_port;   // Source port number
    bit<16> dst_port;   // Destination port number
    bit<16> length;     // Length of UDP header + data
    bit<16> checksum;   // Optional checksum (IPv4 requires)
};

/**
 * IPv4 Transport Header (20 bytes)
 * IPv4 header for UDP encapsulation
 */
header ipv4_header {
    // bit<4> version = 4;  // (pseudocode: field initializer removed)   // IP version (4)
    bit<4> ihl;         // Internet header length
    bit<8> dscp;        // Differentiated services
    bit<16> total_length; // Total packet length
    bit<16> identification; // Identification
    bit<3>  flags;      // Fragmentation flags
    bit<13> frag_offset; // Fragment offset
    bit<8>  ttl;       // Time to live
    // bit<8>  protocol = 17;  // (pseudocode: field initializer removed) // UDP protocol number
    bit<16> header_checksum; // Header checksum
    bit<32> src_addr; // Source IP address
    bit<32> dst_addr; // Destination IP address
};

/**
 * IPv6 Transport Header (40 bytes)
 * IPv6 header for UDP encapsulation
 */
header ipv6_header {
    // bit<4>   version = 6;  // (pseudocode: field initializer removed)   // IP version (6)
    bit<8>   traffic_class; // Traffic class
    bit<20>  flow_label;  // Flow label
    bit<16>  payload_length; // UDP packet length
    // bit<8>   next_header = 17;  // (pseudocode: field initializer removed) // UDP protocol number
    bit<8>   hop_limit;    // Hop limit
    bit<128> src_addr;  // Source IPv6 address
    bit<128> dst_addr;  // Destination IPv6 address
};

/**
 * P4 Parser Logic for UDP
 */
/*
parser udp_parser(packet_in pkt, out headers hdr) {
    state start {
        // Peek IP version to determine encapsulation
        bit<4> ip_version;
        pkt.lookahead(ip_version);
        
        transition select(ip_version) {
            4: parse_ipv4;
            6: parse_ipv6;
            default: accept;
        }
    }
    
    state parse_ipv4 {
        pkt.extract(hdr.ipv4_header);
        transition select(hdr.ipv4_header.protocol) {
            17: parse_udp; // UDP protocol
            default: accept;
        }
    }
    
    state parse_ipv6 {
        pkt.extract(hdr.ipv6_header);
        transition select(hdr.ipv6_header.next_header) {
            17: parse_udp; // UDP protocol
            default: accept;
        }
    }
    
    state parse_udp {
        pkt.extract(hdr.udp_header);
        transition select(hdr.udp_header.dst_port) {
            DNS: parse_dns;
            NTP: parse_ntp;
            default: parse_payload;
        }
    }
    
    // Additional parse states for UDP payloads...
}
*/

/**
 * P4 Match-Action Pipeline for UDP
 */
/*
control udp_control(inout headers hdr) {
    action forward_udp() {
        // Basic UDP forwarding logic
        standard_metadata.egress_spec = 
            routing_table[hdr.ipv4_header.dst_addr];
    }
    
    action calculate_checksum() {
        // Compute UDP checksum (pseudo-header + payload)
        hdr.udp_header.checksum = compute_udp_checksum(
            hdr.ipv4_header.src_addr,
            hdr.ipv4_header.dst_addr,
            hdr.udp_header.length
        );
    }
    
    action validate_length() {
        // Verify UDP length matches IP payload length
        if (hdr.ipv4_header.protocol == 17) {
            verify(hdr.udp_header.length == 
                  hdr.ipv4_header.total_length - hdr.ipv4_header.ihl*4);
        }
    }
    
    table udp_processing {
        key = {
            hdr.udp_header.dst_port: exact;
            hdr.ipv4_header.dst_addr: exact; // For IPv4
            hdr.ipv6_header.dst_addr: exact; // For IPv6
        }
        actions = {
            forward_udp;
            calculate_checksum;
            validate_length;
            NoAction;
        }
        default_action: NoAction;
    }
    
    apply {
        udp_processing.apply();
    }
}
*/