add IP stack simulator

src/IPFrameInfo.hh

@@ -0,0 +1,105 @@
+#pragma once
+
+#include <stdint.h>
+
+#include <phosg/Encoding.hh>
+
+
+
+struct EthernetHeader {
+  uint8_t dest_mac[6];
+  uint8_t src_mac[6];
+  be_uint16_t protocol;
+} __attribute__((packed));
+
+struct ARPHeader {
+  be_uint16_t hardware_type;
+  be_uint16_t protocol_type; // same as EthernetHeader::protocol
+  uint8_t hwaddr_len;
+  uint8_t paddr_len;
+  be_uint16_t operation;
+} __attribute__((packed));
+
+struct IPv4Header {
+  uint8_t version_ihl;
+  uint8_t tos;
+  be_uint16_t size;
+  be_uint16_t id;
+  be_uint16_t frag_offset;
+  uint8_t ttl;
+  uint8_t protocol;
+  be_uint16_t checksum;
+  be_uint32_t src_addr;
+  be_uint32_t dest_addr;
+} __attribute__((packed));
+
+struct UDPHeader {
+  be_uint16_t src_port;
+  be_uint16_t dest_port;
+  be_uint16_t size;
+  be_uint16_t checksum;
+} __attribute__((packed));
+
+struct TCPHeader {
+  enum Flag {
+    NS  = 0x0100,
+    CWR = 0x0080, // congestion window reduced
+    ECE = 0x0040, // ECN capable / congestion experienced
+    URG = 0x0020, // urgent pointer used
+    ACK = 0x0010, // ack_num is valid
+    PSH = 0x0008, // sending data
+    RST = 0x0004, // reset (hard disconnect)
+    SYN = 0x0002, // synchronize sequence numbers (open connection)
+    FIN = 0x0001, // close (normal disconnect)
+  };
+
+  be_uint16_t src_port;
+  be_uint16_t dest_port;
+  be_uint32_t seq_num;
+  be_uint32_t ack_num;
+  be_uint16_t flags;
+  be_uint16_t window;
+  be_uint16_t checksum;
+  be_uint16_t urgent_ptr;
+} __attribute__((packed));
+
+
+
+struct FrameInfo {
+  // This is always valid
+  const EthernetHeader* ether;
+  uint16_t ether_protocol;
+
+  // At most one of these is not null
+  const IPv4Header* ipv4;
+  const ARPHeader* arp;
+
+  // One of these may be not null if this->ipv4 is not null
+  const UDPHeader* udp;
+  const TCPHeader* tcp;
+
+  const void* header_start;
+  const void* payload;
+  size_t total_size;
+  size_t tcp_options_size;
+  size_t payload_size;
+
+  FrameInfo();
+  FrameInfo(const std::string& data);
+  FrameInfo(const void* data, size_t size);
+
+  std::string header_str() const;
+
+  void truncate(size_t new_total_size);
+
+  size_t size_from_header() const;
+
+  static uint16_t computed_ipv4_header_checksum(const IPv4Header& ipv4);
+  uint16_t computed_ipv4_header_checksum() const;
+  static uint16_t computed_udp4_checksum(
+      const IPv4Header& ipv4, const UDPHeader& udp, const void* data, size_t size);
+  uint16_t computed_udp4_checksum() const;
+  static uint16_t computed_tcp4_checksum(
+      const IPv4Header& ip, const TCPHeader& tcp, const void* data, size_t size);
+  uint16_t computed_tcp4_checksum() const;
+};