455 lines
11 KiB
C++
455 lines
11 KiB
C++
// This file is public domain, in case it's useful to anyone. -comex
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// The central server implementation.
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#include <arpa/inet.h>
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#include <cerrno>
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#include <cstdio>
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#include <cstdlib>
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#include <cstring>
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#include <fcntl.h>
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#include <netinet/in.h>
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#include <sys/socket.h>
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#include <sys/time.h>
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#include <sys/types.h>
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#include <unistd.h>
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#include <unordered_map>
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#include <utility>
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#include <vector>
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#include "Common/TraversalProto.h"
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#define DEBUG 1
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#define NUMBER_OF_TRIES 5
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static u64 currentTime;
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struct OutgoingPacketInfo
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{
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TraversalPacket packet;
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TraversalRequestId misc;
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sockaddr_in6 dest;
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int tries;
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u64 sendTime;
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};
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template <typename T>
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struct EvictEntry
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{
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u64 updateTime;
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T value;
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};
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template <typename V>
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struct EvictFindResult
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{
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bool found;
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V* value;
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};
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template <typename K, typename V>
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EvictFindResult<V> EvictFind(std::unordered_map<K, EvictEntry<V>>& map, const K& key,
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bool refresh = false)
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{
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retry:
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const u64 expiryTime = 30 * 1000000; // 30s
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EvictFindResult<V> result;
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if (map.bucket_count())
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{
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auto bucket = map.bucket(key);
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auto it = map.begin(bucket);
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for (; it != map.end(bucket); ++it)
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{
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if (currentTime - it->second.updateTime > expiryTime)
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{
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map.erase(it->first);
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goto retry;
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}
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if (it->first == key)
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{
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if (refresh)
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it->second.updateTime = currentTime;
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result.found = true;
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result.value = &it->second.value;
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return result;
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}
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}
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}
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#if DEBUG
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printf("failed to find key '");
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for (size_t i = 0; i < sizeof(key); i++)
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{
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printf("%02x", ((u8*)&key)[i]);
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}
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printf("'\n");
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#endif
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result.found = false;
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return result;
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}
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template <typename K, typename V>
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V* EvictSet(std::unordered_map<K, EvictEntry<V>>& map, const K& key)
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{
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// can't use a local_iterator to emplace...
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auto& result = map[key];
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result.updateTime = currentTime;
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return &result.value;
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}
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namespace std
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{
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template <>
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struct hash<TraversalHostId>
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{
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size_t operator()(const TraversalHostId& id) const
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{
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auto p = (u32*)id.data();
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return p[0] ^ ((p[1] << 13) | (p[1] >> 19));
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}
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};
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}
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static int sock;
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static int urandomFd;
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static std::unordered_map<TraversalRequestId, OutgoingPacketInfo> outgoingPackets;
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static std::unordered_map<TraversalHostId, EvictEntry<TraversalInetAddress>> connectedClients;
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static TraversalInetAddress MakeInetAddress(const sockaddr_in6& addr)
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{
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if (addr.sin6_family != AF_INET6)
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{
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fprintf(stderr, "bad sockaddr_in6\n");
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exit(1);
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}
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u32* words = (u32*)addr.sin6_addr.s6_addr;
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TraversalInetAddress result = {0};
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if (words[0] == 0 && words[1] == 0 && words[2] == 0xffff0000)
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{
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result.isIPV6 = false;
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result.address[0] = words[3];
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}
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else
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{
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result.isIPV6 = true;
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memcpy(result.address, words, sizeof(result.address));
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}
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result.port = addr.sin6_port;
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return result;
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}
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static sockaddr_in6 MakeSinAddr(const TraversalInetAddress& addr)
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{
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sockaddr_in6 result;
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#ifdef SIN6_LEN
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result.sin6_len = sizeof(result);
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#endif
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result.sin6_family = AF_INET6;
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result.sin6_port = addr.port;
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result.sin6_flowinfo = 0;
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if (addr.isIPV6)
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{
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memcpy(&result.sin6_addr, addr.address, 16);
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}
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else
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{
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u32* words = (u32*)result.sin6_addr.s6_addr;
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words[0] = 0;
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words[1] = 0;
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words[2] = 0xffff0000;
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words[3] = addr.address[0];
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}
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result.sin6_scope_id = 0;
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return result;
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}
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static void GetRandomBytes(void* output, size_t size)
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{
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static u8 bytes[8192];
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static size_t bytesLeft = 0;
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if (bytesLeft < size)
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{
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ssize_t rv = read(urandomFd, bytes, sizeof(bytes));
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if (rv != sizeof(bytes))
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{
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perror("read from /dev/urandom");
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exit(1);
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}
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bytesLeft = sizeof(bytes);
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}
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memcpy(output, bytes + (bytesLeft -= size), size);
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}
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static void GetRandomHostId(TraversalHostId* hostId)
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{
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char buf[9];
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u32 num;
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GetRandomBytes(&num, sizeof(num));
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sprintf(buf, "%08x", num);
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memcpy(hostId->data(), buf, 8);
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}
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static const char* SenderName(sockaddr_in6* addr)
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{
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static char buf[INET6_ADDRSTRLEN + 10];
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inet_ntop(PF_INET6, &addr->sin6_addr, buf, sizeof(buf));
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sprintf(buf + strlen(buf), ":%d", ntohs(addr->sin6_port));
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return buf;
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}
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static void TrySend(const void* buffer, size_t size, sockaddr_in6* addr)
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{
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#if DEBUG
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printf("-> %d %llu %s\n", ((TraversalPacket*)buffer)->type,
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(long long)((TraversalPacket*)buffer)->requestId, SenderName(addr));
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#endif
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if ((size_t)sendto(sock, buffer, size, 0, (sockaddr*)addr, sizeof(*addr)) != size)
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{
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perror("sendto");
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}
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}
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static TraversalPacket* AllocPacket(const sockaddr_in6& dest, TraversalRequestId misc = 0)
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{
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TraversalRequestId requestId;
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GetRandomBytes(&requestId, sizeof(requestId));
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OutgoingPacketInfo* info = &outgoingPackets[requestId];
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info->dest = dest;
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info->misc = misc;
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info->tries = 0;
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info->sendTime = currentTime;
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TraversalPacket* result = &info->packet;
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memset(result, 0, sizeof(*result));
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result->requestId = requestId;
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return result;
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}
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static void SendPacket(OutgoingPacketInfo* info)
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{
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info->tries++;
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info->sendTime = currentTime;
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TrySend(&info->packet, sizeof(info->packet), &info->dest);
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}
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static void ResendPackets()
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{
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std::vector<std::pair<TraversalInetAddress, TraversalRequestId>> todoFailures;
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todoFailures.clear();
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for (auto it = outgoingPackets.begin(); it != outgoingPackets.end();)
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{
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OutgoingPacketInfo* info = &it->second;
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if (currentTime - info->sendTime >= (u64)(300000 * info->tries))
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{
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if (info->tries >= NUMBER_OF_TRIES)
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{
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if (info->packet.type == TraversalPacketPleaseSendPacket)
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{
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todoFailures.push_back(std::make_pair(info->packet.pleaseSendPacket.address, info->misc));
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}
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it = outgoingPackets.erase(it);
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continue;
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}
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else
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{
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SendPacket(info);
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}
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}
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++it;
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}
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for (const auto& p : todoFailures)
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{
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TraversalPacket* fail = AllocPacket(MakeSinAddr(p.first));
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fail->type = TraversalPacketConnectFailed;
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fail->connectFailed.requestId = p.second;
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fail->connectFailed.reason = TraversalConnectFailedClientDidntRespond;
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}
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}
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static void HandlePacket(TraversalPacket* packet, sockaddr_in6* addr)
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{
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#if DEBUG
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printf("<- %d %llu %s\n", packet->type, (long long)packet->requestId, SenderName(addr));
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#endif
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bool packetOk = true;
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switch (packet->type)
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{
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case TraversalPacketAck:
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{
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auto it = outgoingPackets.find(packet->requestId);
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if (it == outgoingPackets.end())
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break;
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OutgoingPacketInfo* info = &it->second;
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if (info->packet.type == TraversalPacketPleaseSendPacket)
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{
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TraversalPacket* ready = AllocPacket(MakeSinAddr(info->packet.pleaseSendPacket.address));
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if (packet->ack.ok)
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{
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ready->type = TraversalPacketConnectReady;
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ready->connectReady.requestId = info->misc;
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ready->connectReady.address = MakeInetAddress(info->dest);
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}
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else
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{
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ready->type = TraversalPacketConnectFailed;
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ready->connectFailed.requestId = info->misc;
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ready->connectFailed.reason = TraversalConnectFailedClientFailure;
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}
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}
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outgoingPackets.erase(it);
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break;
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}
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case TraversalPacketPing:
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{
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auto r = EvictFind(connectedClients, packet->ping.hostId, true);
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packetOk = r.found;
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break;
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}
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case TraversalPacketHelloFromClient:
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{
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u8 ok = packet->helloFromClient.protoVersion <= TraversalProtoVersion;
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TraversalPacket* reply = AllocPacket(*addr);
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reply->type = TraversalPacketHelloFromServer;
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reply->helloFromServer.ok = ok;
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if (ok)
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{
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TraversalHostId hostId;
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TraversalInetAddress* iaddr;
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// not that there is any significant change of
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// duplication, but...
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GetRandomHostId(&hostId);
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while (true)
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{
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auto r = EvictFind(connectedClients, hostId);
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if (!r.found)
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{
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iaddr = EvictSet(connectedClients, hostId);
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break;
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}
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}
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*iaddr = MakeInetAddress(*addr);
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reply->helloFromServer.yourAddress = *iaddr;
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reply->helloFromServer.yourHostId = hostId;
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}
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break;
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}
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case TraversalPacketConnectPlease:
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{
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TraversalHostId& hostId = packet->connectPlease.hostId;
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auto r = EvictFind(connectedClients, hostId);
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if (!r.found)
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{
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TraversalPacket* reply = AllocPacket(*addr);
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reply->type = TraversalPacketConnectFailed;
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reply->connectFailed.requestId = packet->requestId;
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reply->connectFailed.reason = TraversalConnectFailedNoSuchClient;
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}
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else
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{
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TraversalPacket* please = AllocPacket(MakeSinAddr(*r.value), packet->requestId);
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please->type = TraversalPacketPleaseSendPacket;
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please->pleaseSendPacket.address = MakeInetAddress(*addr);
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}
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break;
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}
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default:
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fprintf(stderr, "received unknown packet type %d from %s\n", packet->type, SenderName(addr));
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}
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if (packet->type != TraversalPacketAck)
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{
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TraversalPacket ack = {};
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ack.type = TraversalPacketAck;
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ack.requestId = packet->requestId;
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ack.ack.ok = packetOk;
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TrySend(&ack, sizeof(ack), addr);
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}
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}
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int main()
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{
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int rv;
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urandomFd = open("/dev/urandom", O_RDONLY);
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if (urandomFd < 0)
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{
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perror("open /dev/urandom");
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return 1;
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}
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sock = socket(PF_INET6, SOCK_DGRAM, 0);
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if (sock == -1)
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{
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perror("socket");
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return 1;
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}
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int no = 0;
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rv = setsockopt(sock, IPPROTO_IPV6, IPV6_V6ONLY, &no, sizeof(no));
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if (rv < 0)
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{
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perror("setsockopt IPV6_V6ONLY");
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return 1;
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}
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in6_addr any = IN6ADDR_ANY_INIT;
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sockaddr_in6 addr;
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#ifdef SIN6_LEN
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addr.sin6_len = sizeof(addr);
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#endif
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addr.sin6_family = AF_INET6;
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addr.sin6_port = htons(6262);
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addr.sin6_flowinfo = 0;
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addr.sin6_addr = any;
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addr.sin6_scope_id = 0;
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rv = bind(sock, (sockaddr*)&addr, sizeof(addr));
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if (rv < 0)
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{
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perror("bind");
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return 1;
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}
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timeval tv;
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tv.tv_sec = 0;
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tv.tv_usec = 300000;
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rv = setsockopt(sock, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv));
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if (rv < 0)
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{
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perror("setsockopt SO_RCVTIMEO");
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return 1;
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}
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while (true)
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{
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sockaddr_in6 raddr;
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socklen_t addrLen = sizeof(raddr);
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TraversalPacket packet;
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// note: switch to recvmmsg (yes, mmsg) if this becomes
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// expensive
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rv = recvfrom(sock, &packet, sizeof(packet), 0, (sockaddr*)&raddr, &addrLen);
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if (gettimeofday(&tv, nullptr) < 0)
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{
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perror("gettimeofday");
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exit(1);
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}
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currentTime = (u64)tv.tv_sec * 1000000 + tv.tv_usec;
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if (rv < 0)
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{
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if (errno != EINTR && errno != EAGAIN)
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{
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perror("recvfrom");
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return 1;
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}
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}
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else if ((size_t)rv < sizeof(packet))
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{
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fprintf(stderr, "received short packet from %s\n", SenderName(&raddr));
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}
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else
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{
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HandlePacket(&packet, &raddr);
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}
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ResendPackets();
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}
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}
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