Add IPv4 definitions and helpers

ip.cc

@@ -0,0 +1,38 @@
+/*
+ * Copyright (C) 2014 Cloudius Systems, Ltd.
+ *
+ */
+
+#include "ip.hh"
+
+namespace net {
+
+uint16_t ip_checksum(void* data, size_t len) {
+    uint64_t csum = 0;
+    auto p64 = reinterpret_cast<uint64_t*>(data);
+    while (len >= 8) {
+        auto old = csum;
+        csum += ntohq(*p64++);
+        csum += (csum < old);
+        len -= 8;
+    }
+    auto p16 = reinterpret_cast<uint16_t*>(p64);
+    while (len >= 2) {
+        auto old = csum;
+        csum += ntohs(*p16++);
+        csum += (csum < old);
+        len -= 2;
+    }
+    auto p8 = reinterpret_cast<uint16_t*>(p16);
+    if (len) {
+        auto old = csum;
+        csum += *p8++;
+        csum += (csum < old);
+        len -= 1;
+    }
+    csum = (csum & 0xffff) + ((csum >> 16) & 0xffff) + ((csum >> 32) & 0xffff) + (csum >> 48);
+    csum += csum >> 16;
+    return htons(~csum);
+}
+
+}

ip.hh

@@ -0,0 +1,107 @@
+/*
+ * Copyright (C) 2014 Cloudius Systems, Ltd.
+ *
+ */
+
+#ifndef IP_HH_
+#define IP_HH_
+
+#include <arpa/inet.h>
+#include <cstdint>
+#include <array>
+
+namespace net {
+
+inline uint64_t ntohq(uint64_t v) {
+    return __builtin_bswap64(v);
+}
+
+uint16_t ip_checksum(void* data, size_t len);
+
+inline void ntoh() {}
+inline void hton() {}
+
+inline void ntoh(uint16_t& x) { x = ntohs(x); }
+inline void hton(uint16_t& x) { x = htons(x); }
+inline void ntoh(uint32_t& x) { x = ntohl(x); }
+inline void hton(uint32_t& x) { x = htonl(x); }
+
+// gcc (correctly) won't bind a packed uint16_t to a reference,
+// so bypass it by sending a pointer.
+// FIXME: this is broken on machines that don't support unaligned
+// loads with the normal instructions.
+inline void ntoh(uint16_t* x) { *x = ntohs(*x); }
+inline void hton(uint16_t* x) { *x = htons(*x); }
+inline void ntoh(uint32_t* x) { *x = ntohl(*x); }
+inline void hton(uint32_t* x) { *x = htonl(*x); }
+
+template <typename First, typename... Rest>
+inline
+void ntoh(First&& first, Rest&&... rest) {
+    ntoh(*(std::remove_reference_t<First>*)&first);
+    ntoh(std::forward<Rest>(rest)...);
+}
+
+template <typename First, typename... Rest>
+inline
+void hton(First&& first, Rest... rest) {
+    hton(*(std::remove_reference_t<First>*)&first);
+    hton(std::forward<Rest>(rest)...);
+}
+
+template <class T>
+inline
+void ntoh(T& x) {
+    x.adjust_endianness([] (auto&&... what) { ntoh(std::forward<decltype(what)>(what)...); });
+}
+
+template <class T>
+inline
+void hton(T& x) {
+    x.adjust_endianness([] (auto&&... what) { hton(std::forward<decltype(what)>(what)...); });
+}
+
+struct eth_hdr {
+    std::array<uint8_t, 6> dst_mac;
+    std::array<uint8_t, 6>  src_mac;
+    uint16_t eth_proto;
+    template <typename Adjuster>
+    auto adjust_endianness(Adjuster a) {
+        return a(&eth_proto);
+    }
+} __attribute__((packed));
+
+struct ip_hdr {
+    uint8_t ihl : 4;
+    uint8_t ver : 4;
+    uint8_t dscp : 6;
+    uint8_t ecn : 2;
+    uint16_t len;
+    uint16_t id;
+    uint16_t frag;
+    uint8_t ttl;
+    uint8_t ip_proto;
+    uint16_t csum;
+    uint32_t src_ip;
+    uint32_t dst_ip;
+    uint8_t options[0];
+    template <typename Adjuster>
+    auto adjust_endianness(Adjuster a) {
+        return a(&len, &id, &frag, &csum, &src_ip, &dst_ip);
+    }
+} __attribute__((packed));
+
+struct icmp_hdr {
+    uint8_t type;
+    uint8_t code;
+    uint16_t csum;
+    uint32_t rest;
+    template <typename Adjuster>
+    auto adjust_endianness(Adjuster a) {
+        return a(csum);
+    }
+} __attribute__((packed));
+
+}
+
+#endif /* IP_HH_ */