Split UdpVpn in -Client and -Server flavour

Makefile

@@ -2,7 +2,11 @@ CXX=g++
 CXXFLAGS=-O2 -g -Wall -Wextra -std=c++17
 CXXLIBS=
 
-OBJS=UdpVpn.o VpnPeer.o TunDevice.o ip_header.o util.o main.o
+OBJS= \
+	  UdpVpn.o UdpVpnClient.o UdpVpnServer.o \
+	  VpnPeer.o \
+	  TunDevice.o \
+	  ip_header.o util.o main.o
 TARGET=congestvpn
 
 all: $(TARGET)

UdpVpn.cpp

@@ -9,12 +9,11 @@
 #include <poll.h>
 #include <errno.h>
 
-UdpVpn::UdpVpn()
-    : _bound(false), _stopped(false), _has_peer(false), _tun_dev("cvpn%d")
-{
-    memset(&_serv_addr, 0, sizeof(_serv_addr));
-    memset(&_peer_addr, 0, sizeof(_peer_addr));
+#include "ip_header.hpp"
 
+UdpVpn::UdpVpn()
+    : _stopped(false), _tun_dev("cvpn%d")
+{
     _socket = socket(AF_INET6, SOCK_DGRAM, 0);
     if(_socket < 0)
         throw UdpVpn::InitializationError("Cannot create socket", errno, true);
@@ -24,36 +23,6 @@ UdpVpn::~UdpVpn() {
     close(_socket);
 }
 
-void UdpVpn::bind(in_port_t port) {
-    bind(in6addr_any, port);
-}
-void UdpVpn::bind(const struct in6_addr& bind_addr6, in_port_t port) {
-    int rc;
-
-    _serv_addr.sin6_family = AF_INET6;
-    _serv_addr.sin6_port = htons(port);
-    _serv_addr.sin6_addr = bind_addr6;
-
-    rc = ::bind(
-            _socket, (const struct sockaddr*)&_serv_addr, sizeof(_serv_addr));
-    if(rc < 0) {
-        throw UdpVpn::InitializationError("Cannot bind socket", errno, true);
-    }
-
-    debugf("> Listening on port %d\n", port);
-    _bound = true;
-}
-
-void UdpVpn::set_peer(const sockaddr_in6& peer_addr) {
-    memcpy(&_peer_addr, &peer_addr, sizeof(_peer_addr));
-    _has_peer = true;
-
-    char peer_addr_str[INET6_ADDRSTRLEN];
-    inet_ntop(
-            AF_INET6, &(peer_addr.sin6_addr), peer_addr_str, INET6_ADDRSTRLEN);
-    debugf("Set peer to %s:%d\n", peer_addr_str, ntohs(peer_addr.sin6_port));
-}
-
 void UdpVpn::run() {
     int rc;
     int start_at_fd = 0;  // read from polled fds in round-robin fashion
@@ -98,63 +67,40 @@ void UdpVpn::run() {
     }
 }
 
-void UdpVpn::receive_from_tun() {
+size_t UdpVpn::read_from_tun(char* buffer, size_t len) {
     // We know that there is data available -- use `read()`
-    char buffer[1500];
-    size_t nread = _tun_dev.read(buffer, 1500);
+    size_t nread = _tun_dev.read(buffer, len);
 
     if(nread == 0)
-        return;
+        return 0;
 
-    kdebugf("Transmitting packet of size %d to peer\n", nread);
-    send_over_udp(buffer, nread);
+    return nread;
 }
 
-void UdpVpn::receive_from_udp() {
+size_t UdpVpn::read_from_udp(char* buffer, size_t len,
+        sockaddr_in6& peer_addr)
+{
     ssize_t nread;
-    char buffer[1500];
-    struct sockaddr_in6 peer_addr;
     socklen_t peer_addr_len = sizeof(peer_addr);
-
-    nread = recvfrom(_socket, buffer, 1500, MSG_WAITALL,
+    nread = recvfrom(_socket, buffer, len, MSG_WAITALL,
             (struct sockaddr*) &peer_addr, &peer_addr_len);
 
     if(nread < 0)
         throw UdpVpn::NetError("Cannot receive datagram", errno, true);
     if(nread == 0)
-        return;
+        return 0;
 
     if(peer_addr.sin6_family != AF_INET6) {
         debugf("WARNING: Received non-ipv6 family datagram %d. Ignoring.\n",
                 peer_addr.sin6_family);
-        return;
+        return 0;
     }
     if(peer_addr_len != sizeof(peer_addr)) {
         debugf("WARNING: received unexpected source address length %u."
                 "Ignoring.\n",
                 peer_addr_len);
-        return;
-    }
-
-    set_peer(peer_addr);
-
-    // Reinject into tun
-    kdebugf("Receiving packet of size %d from peer\n", nread);
-    _tun_dev.write(buffer, nread);
-}
-
-size_t UdpVpn::send_over_udp(const char* data, size_t len) {
-    ssize_t nsent;
-
-    if(!_has_peer) {
-        debugf("Dropping packet to be transmitted: no peer.\n");
         return 0;
     }
 
-    nsent = sendto(_socket, data, len, MSG_CONFIRM,
-            (const struct sockaddr*) &_peer_addr, sizeof(_peer_addr));
-    if(nsent < 0)
-        throw NetError("Could not send UDP packet", errno, true);
-
-    return (size_t) nsent;
+    return nread;
 }

UdpVpn.hpp

@@ -5,6 +5,7 @@
 
 #include "util.hpp"
 #include "TunDevice.hpp"
+#include "VpnPeer.hpp"
 
 /** Handles UDP communication */
 
@@ -28,18 +29,10 @@ class UdpVpn {
         };
 
         UdpVpn();
-        ~UdpVpn();
-
-        void bind(in_port_t port);
-        void bind(const struct in6_addr& bind_addr6, in_port_t port);
+        virtual ~UdpVpn();
 
         int get_socket_fd() const { return _socket; }
         const TunDevice& get_tun_dev() const { return _tun_dev; }
-        bool is_bound() const { return _bound; }
-
-        // Sets the peer address
-        void set_peer(const sockaddr_in6& peer_addr);
-        void unset_peer() { _has_peer = false; }
 
         // Run the server.
         void run();
@@ -48,17 +41,14 @@ class UdpVpn {
         void stop() { _stopped = true; }
 
     protected:
-        void receive_from_tun();
-        void receive_from_udp();
+        virtual void receive_from_tun() = 0;
+        virtual void receive_from_udp() = 0;
 
-        size_t send_over_udp(const char* data, size_t len);
+        size_t read_from_tun(char* buffer, size_t len);
+        size_t read_from_udp(char* buffer, size_t len, sockaddr_in6& peer_addr);
 
-    private:
         int _socket;
-        bool _bound;
         bool _stopped;
-        bool _has_peer;
-        struct sockaddr_in6 _serv_addr, _peer_addr;
 
         TunDevice _tun_dev;
 };

UdpVpnClient.cpp

@@ -0,0 +1,67 @@
+#include <cstring>
+
+#include "UdpVpnClient.hpp"
+#include "ip_header.hpp"
+
+UdpVpnClient::UdpVpnClient(const struct sockaddr_in6& server) : UdpVpn() {
+    memset(&_server_addr, 0, sizeof(_server_addr));
+    set_server(server);
+}
+
+void UdpVpnClient::set_server(const struct sockaddr_in6& server_addr) {
+    if(server_addr.sin6_family != AF_INET6)
+        throw UdpVpn::InitializationError("Server address must be IPv6");
+
+    memcpy(&_server_addr, &server_addr, sizeof(_server_addr));
+}
+
+void UdpVpnClient::receive_from_tun() {
+    char buffer[1500];
+    size_t nread = read_from_tun(buffer, 1500);
+    if(nread == 0)
+        return;
+
+    // Parse inner packet header -- assume IPv6 for now [FIXME]
+    IPv6Header inner_header;
+    if(!parse_ipv6_header(buffer, nread, inner_header)) {
+        // Not a valid header -- ignore the packet
+        debugf("Ignoring outgoing packet with invalid header\n");
+        return;
+    }
+
+    kdebugf("Transmitting %s -> %s, size %d\n",
+            format_address(inner_header.source.s6_addr),
+            format_address(inner_header.dest.s6_addr),
+            nread);
+
+    write_to_server(buffer, nread);
+}
+
+void UdpVpnClient::receive_from_udp() {
+    char buffer[1500];
+    sockaddr_in6 peer_addr;
+    size_t nread = read_from_udp(buffer, 1500, peer_addr);
+
+    // Parse inner packet header -- assume IPv6 for now [FIXME]
+    IPv6Header inner_header;
+    if(!parse_ipv6_header(buffer, nread, inner_header)) {
+        // Not a valid header -- ignore the packet
+        debugf("Ignoring packet with invalid header\n");
+        return;
+    }
+
+    // Reinject into tun
+    kdebugf("Receiving packet of size %d from peer\n", nread);
+    _tun_dev.write(buffer, nread);
+}
+
+size_t UdpVpnClient::write_to_server(const char* data, size_t len) {
+    ssize_t nsent;
+
+    nsent = sendto(_socket, data, len, MSG_CONFIRM,
+            (const struct sockaddr*) &_server_addr, sizeof(_server_addr));
+    if(nsent < 0)
+        throw NetError("Could not send UDP packet", errno, true);
+
+    return (size_t) nsent;
+}

UdpVpnClient.hpp

@@ -0,0 +1,18 @@
+#pragma once
+
+#include "UdpVpn.hpp"
+
+class UdpVpnClient: public UdpVpn {
+    public:
+        UdpVpnClient(const struct sockaddr_in6& server);
+
+    protected:
+        void set_server(const struct sockaddr_in6& server_addr);
+
+        virtual void receive_from_tun();
+        virtual void receive_from_udp();
+
+        size_t write_to_server(const char* data, size_t len);
+
+        struct sockaddr_in6 _server_addr;
+};

UdpVpnServer.cpp

@@ -0,0 +1,104 @@
+#include <cstring>
+
+#include "UdpVpnServer.hpp"
+#include "ip_header.hpp"
+
+UdpVpnServer::UdpVpnServer(in_port_t port) : UdpVpn() {
+    memset(&_bind_addr, 0, sizeof(_bind_addr));
+    bind(in6addr_any, port);
+}
+
+UdpVpnServer::UdpVpnServer(const struct in6_addr& bind_addr6, in_port_t port)
+    : UdpVpn()
+{
+    memset(&_bind_addr, 0, sizeof(_bind_addr));
+    bind(bind_addr6, port);
+}
+
+void UdpVpnServer::bind(const struct in6_addr& bind_addr6, in_port_t port) {
+    int rc;
+
+    _bind_addr.sin6_family = AF_INET6;
+    _bind_addr.sin6_port = htons(port);
+    _bind_addr.sin6_addr = bind_addr6;
+
+    rc = ::bind(
+            _socket, (const struct sockaddr*)&_bind_addr, sizeof(_bind_addr));
+    if(rc < 0) {
+        throw UdpVpn::InitializationError("Cannot bind socket", errno, true);
+    }
+
+    debugf("> Listening on port %d\n", port);
+}
+
+
+std::shared_ptr<VpnPeer> UdpVpnServer::get_peer_for_ip(
+        const in6_addr& peer_addr)
+{
+    auto peer_iter = _peers.find(peer_addr);
+    if(peer_iter == _peers.end()) // Unknown peer
+        return nullptr;
+    return peer_iter->second;
+}
+
+void UdpVpnServer::receive_from_tun() {
+    char buffer[1500];
+    size_t nread = read_from_tun(buffer, 1500);
+    if(nread == 0)
+        return;
+
+    // Parse inner packet header -- assume IPv6 for now [FIXME]
+    IPv6Header inner_header;
+    if(!parse_ipv6_header(buffer, nread, inner_header)) {
+        // Not a valid header -- ignore the packet
+        debugf("Ignoring outgoing packet with invalid header\n");
+        return;
+    }
+
+    // Recover VpnPeer -- or drop if new
+    std::shared_ptr<VpnPeer> peer = get_peer_for_ip(inner_header.dest);
+    if(!peer) {
+        debugf("Dropping packet for destination %s -- unknown peer.\n",
+                format_address(inner_header.dest.s6_addr));
+        return;
+    }
+
+    kdebugf("Transmitting %s -> %s, size %d\n",
+            format_address(inner_header.source.s6_addr),
+            format_address(inner_header.dest.s6_addr),
+            nread);
+    peer->write(buffer, nread);
+}
+
+void UdpVpnServer::receive_from_udp() {
+    char buffer[1500];
+    sockaddr_in6 peer_addr;
+    size_t nread = read_from_udp(buffer, 1500, peer_addr);
+
+    // Parse inner packet header -- assume IPv6 for now [FIXME]
+    IPv6Header inner_header;
+    if(!parse_ipv6_header(buffer, nread, inner_header)) {
+        // Not a valid header -- ignore the packet
+        debugf("Ignoring packet with invalid header\n");
+        return;
+    }
+
+    // Recover VpnPeer -- or create if new
+    std::shared_ptr<VpnPeer> peer = get_peer_for_ip(inner_header.source);
+    if(!peer) {
+        peer = std::make_shared<VpnPeer>(this, peer_addr, inner_header.source);
+        auto insert_result = _peers.insert({inner_header.source, peer});
+
+        debugf("Got new peer %s:%d -- %s [really inserted=%d]\n",
+                format_address(peer_addr.sin6_addr.s6_addr),
+                htons(peer_addr.sin6_port),
+                format_address(inner_header.source.s6_addr),
+                insert_result.second);
+    }
+    // VpnPeer* peer = (peer_iter->second);
+    // TODO -- pass the packet to `peer` for a cleaner flow
+
+    // Reinject into tun
+    kdebugf("Receiving packet of size %d from peer\n", nread);
+    _tun_dev.write(buffer, nread);
+}

UdpVpnServer.hpp

@@ -0,0 +1,23 @@
+#pragma once
+
+#include <unordered_map>
+#include <memory>
+
+#include "UdpVpn.hpp"
+
+class UdpVpnServer: public UdpVpn {
+    public:
+        UdpVpnServer(in_port_t port);
+        UdpVpnServer(const struct in6_addr& bind_addr6, in_port_t port);
+    protected:
+        void bind(const struct in6_addr& bind_addr6, in_port_t port);
+
+        /** Get the peer associated to this (internal) IP. */
+        std::shared_ptr<VpnPeer> get_peer_for_ip(const in6_addr& peer_addr);
+
+        virtual void receive_from_tun();
+        virtual void receive_from_udp();
+
+        struct sockaddr_in6 _bind_addr;
+        std::unordered_map<in6_addr, std::shared_ptr<VpnPeer>> _peers;
+};

main.cpp

@@ -5,6 +5,8 @@
 #include <string.h>
 
 #include "UdpVpn.hpp"
+#include "UdpVpnServer.hpp"
+#include "UdpVpnClient.hpp"
 #include "util.hpp"
 
 struct ProgOptions {
@@ -91,32 +93,40 @@ int main(int argc, char** argv) {
     signal(SIGINT, stop_sig_handler);
 
     try {
-        UdpVpn vpn;
-        vpn_instance = &vpn;
-
-        if(program_options.listen) {
-            vpn.bind(program_options.bind_addr, program_options.bind_port);
+        if(program_options.listen && program_options.has_peer) {
+            fprintf(stderr,
+                    "ERROR: Cannot be a server and a client at the same time "
+                    "-- provide either -l or -s.\n");
+            return 1;
         }
-
-        if(program_options.has_peer) {
+        if(program_options.listen) {
+            vpn_instance = new UdpVpnServer(
+                program_options.bind_addr, program_options.bind_port);
+        } else if(program_options.has_peer) {
             if(program_options.server_port == 0) {
                 fprintf(stderr,
-                        "Initial peer set without a port -- ignoring.\n");
-            }
-            else {
-                struct sockaddr_in6 server_addr;
-                server_addr.sin6_family = AF_INET6;
-                memcpy(&server_addr.sin6_addr,
-                        &program_options.server_addr,
-                        sizeof(server_addr.sin6_addr));
-                server_addr.sin6_port = htons(program_options.server_port);
-                vpn.set_peer(server_addr);
+                        "ERROR: A client instance must be given a server port "
+                        "-- please provide -p.\n");
+                return 1;
             }
+
+            struct sockaddr_in6 server_addr;
+            server_addr.sin6_family = AF_INET6; memcpy(&server_addr.sin6_addr, &program_options.server_addr,
+                    sizeof(server_addr.sin6_addr));
+            server_addr.sin6_port = htons(program_options.server_port);
+
+            vpn_instance = new UdpVpnClient(server_addr);
+        } else {
+            fprintf(stderr,
+                    "ERROR: Must be either a server or a client "
+                    "-- provide either -l or -s.\n");
+            return 1;
         }
 
         printf("Starting to listen...\n");
-        vpn.run();
-        vpn_instance = nullptr;
+        vpn_instance->run();
+
+        delete vpn_instance;
 
         printf("Shutting down.\n");
     } catch(const TunDevice::InitializationError& exn) {