Implement basic server/client + protocol

Includes WireGuard submodule to use the embeddable library

Squashed commit of the following:

commit 3e5252d93c87c4cddf596d4030d736e2cea81557
Author: Tushar Pankaj <tushar.s.pankaj@gmail.com>
Date:   Mon Nov 12 18:33:33 2018 -0600

    Implement server check iface

    Signed-off-by: Tushar Pankaj <tushar.s.pankaj@gmail.com>

commit a30c60e51ecae887fd89654bdedddcf0decb766c
Author: Tushar Pankaj <tushar.s.pankaj@gmail.com>
Date:   Mon Nov 12 18:26:57 2018 -0600

    Add WireGuard embeddable library

    Signed-off-by: Tushar Pankaj <tushar.s.pankaj@gmail.com>

commit ea6ab8ce09d4e84440185536f7b3e92346789233
Author: Tushar Pankaj <tushar.s.pankaj@gmail.com>
Date:   Mon Nov 12 17:59:39 2018 -0600

    Working client and server comms

    Signed-off-by: Tushar Pankaj <tushar.s.pankaj@gmail.com>

commit 5d717e37baaa9882ea2356fa24a2b85beaf51558
Author: Tushar Pankaj <tushar.s.pankaj@gmail.com>
Date:   Mon Nov 12 17:13:32 2018 -0600

    Add IP addr structs to protocol

    Signed-off-by: Tushar Pankaj <tushar.s.pankaj@gmail.com>

commit 8c31eec08257f77a9c95c7437b21bf7eb8106916
Author: Tushar Pankaj <tushar.s.pankaj@gmail.com>
Date:   Mon Nov 12 17:06:18 2018 -0600

    Style fixes

    Signed-off-by: Tushar Pankaj <tushar.s.pankaj@gmail.com>

commit 64f825db92ce31102b29ac96fd382ac3643fb6ae
Author: Tushar Pankaj <tushar.s.pankaj@gmail.com>
Date:   Mon Nov 12 17:06:07 2018 -0600

    Write client connect_to_server

    Signed-off-by: Tushar Pankaj <tushar.s.pankaj@gmail.com>

commit f33225d130263eea481e28269b6b01a7cf75b0c8
Author: Tushar Pankaj <tushar.s.pankaj@gmail.com>
Date:   Fri Nov 9 20:00:37 2018 -0600

    Add pthread library

    Signed-off-by: Tushar Pankaj <tushar.s.pankaj@gmail.com>

commit 1f73168641d92917dc942c3d6cc200fb7f557674
Merge: 98fe966 3048896
Author: Tushar Pankaj <tushar.s.pankaj@gmail.com>
Date:   Wed Nov 7 10:59:13 2018 -0600

    Merge branch 'master' into tp/protocol_draft

commit 98fe966940eaf324b5d8d1edc64f6d0ff1334441
Author: Tushar Pankaj <tushar.s.pankaj@gmail.com>
Date:   Wed Nov 7 10:55:53 2018 -0600

    Add Makefile library includes for capnp

    Signed-off-by: Tushar Pankaj <tushar.s.pankaj@gmail.com>

commit 3bd7dffda7db8e9bf4cd0dad2455328508efb9b2
Author: Tushar Pankaj <tushar.s.pankaj@gmail.com>
Date:   Wed Nov 7 10:49:50 2018 -0600

    Make protocol.capnp.o compile

    Signed-off-by: Tushar Pankaj <tushar.s.pankaj@gmail.com>

commit 14e708783433816fd6cead46e2aa823ab8e41294
Author: Tushar Pankaj <tushar.s.pankaj@gmail.com>
Date:   Wed Nov 7 10:38:29 2018 -0600

    Untested first draft of protocol.capnp

    Signed-off-by: Tushar Pankaj <tushar.s.pankaj@gmail.com>

commit 5558c37a1a2626beaee5bb69c83d4013f2bcaf44
Author: Tushar Pankaj <tushar.s.pankaj@gmail.com>
Date:   Tue Nov 6 20:51:49 2018 -0600

    Exclude capnproto from clang-format

    Signed-off-by: Tushar Pankaj <tushar.s.pankaj@gmail.com>

commit 50042af6aec61c495c08d1b83f4c63288a30cc90
Author: Tushar Pankaj <tushar.s.pankaj@gmail.com>
Date:   Wed Oct 31 20:40:23 2018 -0500

    Make better var names

    Signed-off-by: Tushar Pankaj <tushar.s.pankaj@gmail.com>

commit 2352cbc91e6be9bcd73ca2794372b1ed8361448e
Author: Tushar Pankaj <tushar.s.pankaj@gmail.com>
Date:   Wed Oct 31 20:08:05 2018 -0500

    First draft of protocol

    Signed-off-by: Tushar Pankaj <tushar.s.pankaj@gmail.com>

16 files changed, 510 insertions, 23 deletions

diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 0000000..2c0078c
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,3 @@
+[submodule "WireGuard"]
+	path = WireGuard
+	url = git://git.zx2c4.com/WireGuard
diff --git a/Makefile b/Makefile
index 1e95e47..0c47913 100644
--- a/Makefile
+++ b/Makefile
@@ -1,27 +1,41 @@
 CC ?= gcc
+LIBRARY_INCLUDES = 
+LIBRARY_LDFLAGS = -D_REENTRANT -lpthread -lcapnp_c
 CFLAGS_DEBUG = -g -Wall -Wextra -std=gnu11 -fsanitize=address -fsanitize=leak\
 	-fsanitize=undefined
 LDFLAGS_DEBUG = -fsanitize=address -fsanitize=leak -fsanitize=undefined
 CFLAGS_OPT = -std=gnu11 -O2 -pipe -DNDEBUG
 LDFLAGS_OPT =
-CFLAGS ?= ${CFLAGS_DEBUG}
-LDFLAGS ?= ${LDFLAGS_DEBUG}
+CFLAGS ?= ${CFLAGS_DEBUG} ${LIBRARY_INCLUDES}
+LDFLAGS ?= ${LDFLAGS_DEBUG} ${LIBRARY_LDFLAGS}
 .PHONY: clean style
 PROGS = wg-dynamic-client wg-dynamic-server
-CLIENT_OBJS = wg_dynamic_client.o client.o
-SERVER_OBJS = wg_dynamic_server.o server.o
+CLIENT_OBJS = wg_dynamic_client.o client.o protocol.capnp.o wireguard.o
+SERVER_OBJS = wg_dynamic_server.o server.o protocol.capnp.o wireguard.o
 all: ${PROGS}
 
 wg-dynamic-client: ${CLIENT_OBJS}
 	${CC} ${LDFLAGS} ${CLIENT_OBJS} -o $@
 wg-dynamic-server: ${SERVER_OBJS}
 	${CC} ${LDFLAGS} ${SERVER_OBJS} -o $@
+
 wg_dynamic_client.o: wg_dynamic_client.c client.h
-client.o: client.c client.h
+client.o: client.c client.h wireguard.h
 wg_dynamic_server.o: wg_dynamic_server.c server.h
-server.o: server.c server.h
+server.o: server.c server.h wireguard.h
+wireguard.o: wireguard.c wireguard.h
+protocol.capnp.o: protocol.capnp.c
+
+# capnproto
+protocol.capnp.h: protocol.capnp.c
+	;
+protocol.capnp.c: protocol.capnp
+	capnpc protocol.capnp -oc
+%.capnp: ;
 
 clean:
 	rm -f ${PROGS} *.o *~
 style:
-	clang-format -i --style=file *.c *.h
+	find . -path ./WireGuard -prune -o -type f \( -name "*.c" -or \
+	-name "*.h" \) -and -not \( -name "*.capnp.c" -or \
+	-name "*.capnp.h" \) -print | xargs clang-format -i --style=file
diff --git a/README.md b/README.md
index 0a4f3da..e42b809 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,11 @@
 # Wireguard Dynamic IP Configuration Tool
 
 This is a work-in-progress (i.e. nonexistent) configuration tool for dynamic IPs in Wireguard. There will eventually be stuff here.
+
+## Dependencies
+* Wireguard
+* [libcapnp_c](https://github.com/opensourcerouting/c-capnproto)
+
+## Building
+1. git submodule update --init --recursive
+2. `make`
diff --git a/WireGuard b/WireGuard
new file mode 160000
+Subproject 1b6d93db9a309840bcd7bb67a6bf3e8ca188003
diff --git a/client.c b/client.c
index 2c2f091..ebef8b3 100644
--- a/client.c
+++ b/client.c
@@ -3,8 +3,49 @@
  * Copyright (C) 2018 Wireguard LLC
  */
 
-int connect_to_server(const char interface[])
+#include <stdlib.h>
+#include <stdbool.h>
+#include <unistd.h>
+#include <errno.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <arpa/inet.h>
+#include "protocol.h"
+#include "client.h"
+
+bool is_server_in_allowed_ips(const char iface[])
+{
+	/* TODO: check if IP is in wg allowed ips, etc */
+	return true;
+}
+
+int connect_to_server()
+{
+	int sock = -1;
+	int ret;
+	struct sockaddr_in6 addr;
+
+	sock = socket(AF_INET6, SOCK_STREAM, 0);
+	if (sock < 0) {
+		return -errno;
+	}
+	addr.sin6_family = AF_INET6;
+	addr.sin6_port = htons(WG_DYNAMIC_SERVER_PORT);
+	inet_pton(AF_INET6, WG_DYNAMIC_SERVER_IP, &addr.sin6_addr);
+	ret = connect(sock, (struct sockaddr *)&addr, sizeof(addr));
+	if (ret < 0) {
+		return -errno;
+	}
+
+	return sock;
+}
+
+int close_connection(int sock)
 {
-	/* TODO */
-	return -1;
+	int ret;
+	ret = close(sock);
+	if (ret < 0) {
+		return -errno;
+	}
+	return 0;
 }
diff --git a/client.h b/client.h
index 996cb58..5a4b460 100644
--- a/client.h
+++ b/client.h
@@ -6,6 +6,10 @@
 #ifndef CLIENT_H
 #define CLIENT_H
 
-int connect_to_server(const char interface[]);
+#include <stdbool.h>
+
+bool is_server_in_allowed_ips(const char iface[]);
+int connect_to_server();
+int close_connection(int sock);
 
 #endif
diff --git a/protocol.capnp b/protocol.capnp
new file mode 100644
index 0000000..69f5db4
--- /dev/null
+++ b/protocol.capnp
@@ -0,0 +1,34 @@
+# SPDX-License-Identifier: MIT
+#
+# Copyright (C) 2018 Wireguard LLC
+#
+
+@0xed77208fb3340cc1;
+
+# client request message
+struct WgClientMsg {
+       request @0 :WgClientRequestType;
+       
+       enum WgClientRequestType {
+            simple @0;
+       }
+}
+
+# IPv4 address
+struct WgIpv4Addr {
+       addr @0 :UInt32; # IPv4 address
+       cidr @1 :UInt8; # CIDR of IPv4 address
+}
+
+# IPv6 address
+struct WgIpv6Addr {
+       addr @0 :Data; # IPv6 address
+       cidr @1: UInt8; # CIDR of IPv6 address
+}
+
+# server response message
+struct WgServerSimpleMsg {
+       leasedIpv4 @0 :WgIpv4Addr; # dynamic IPv4 leased to client
+       leaseTimeout @1 :UInt32; # activity timeout for the IP lease in seconds
+       ipv4Routes @2 :List(WgIpv4Addr); # IPv4 routes for client
+}
diff --git a/protocol.capnp.c b/protocol.capnp.c
new file mode 100644
index 0000000..b13f7c6
--- /dev/null
+++ b/protocol.capnp.c
@@ -0,0 +1,142 @@
+#include "protocol.capnp.h"
+/* AUTO GENERATED - DO NOT EDIT */
+#ifdef __GNUC__
+# define capnp_unused __attribute__((unused))
+# define capnp_use(x) (void) x;
+#else
+# define capnp_unused
+# define capnp_use(x)
+#endif
+
+
+WgClientMsg_ptr new_WgClientMsg(struct capn_segment *s) {
+	WgClientMsg_ptr p;
+	p.p = capn_new_struct(s, 8, 0);
+	return p;
+}
+WgClientMsg_list new_WgClientMsg_list(struct capn_segment *s, int len) {
+	WgClientMsg_list p;
+	p.p = capn_new_list(s, len, 8, 0);
+	return p;
+}
+void read_WgClientMsg(struct WgClientMsg *s capnp_unused, WgClientMsg_ptr p) {
+	capn_resolve(&p.p);
+	capnp_use(s);
+	s->request = (enum WgClientMsg_WgClientRequestType)(int) capn_read16(p.p, 0);
+}
+void write_WgClientMsg(const struct WgClientMsg *s capnp_unused, WgClientMsg_ptr p) {
+	capn_resolve(&p.p);
+	capnp_use(s);
+	capn_write16(p.p, 0, (uint16_t) (s->request));
+}
+void get_WgClientMsg(struct WgClientMsg *s, WgClientMsg_list l, int i) {
+	WgClientMsg_ptr p;
+	p.p = capn_getp(l.p, i, 0);
+	read_WgClientMsg(s, p);
+}
+void set_WgClientMsg(const struct WgClientMsg *s, WgClientMsg_list l, int i) {
+	WgClientMsg_ptr p;
+	p.p = capn_getp(l.p, i, 0);
+	write_WgClientMsg(s, p);
+}
+
+WgIpv4Addr_ptr new_WgIpv4Addr(struct capn_segment *s) {
+	WgIpv4Addr_ptr p;
+	p.p = capn_new_struct(s, 8, 0);
+	return p;
+}
+WgIpv4Addr_list new_WgIpv4Addr_list(struct capn_segment *s, int len) {
+	WgIpv4Addr_list p;
+	p.p = capn_new_list(s, len, 8, 0);
+	return p;
+}
+void read_WgIpv4Addr(struct WgIpv4Addr *s capnp_unused, WgIpv4Addr_ptr p) {
+	capn_resolve(&p.p);
+	capnp_use(s);
+	s->addr = capn_read32(p.p, 0);
+	s->cidr = capn_read8(p.p, 4);
+}
+void write_WgIpv4Addr(const struct WgIpv4Addr *s capnp_unused, WgIpv4Addr_ptr p) {
+	capn_resolve(&p.p);
+	capnp_use(s);
+	capn_write32(p.p, 0, s->addr);
+	capn_write8(p.p, 4, s->cidr);
+}
+void get_WgIpv4Addr(struct WgIpv4Addr *s, WgIpv4Addr_list l, int i) {
+	WgIpv4Addr_ptr p;
+	p.p = capn_getp(l.p, i, 0);
+	read_WgIpv4Addr(s, p);
+}
+void set_WgIpv4Addr(const struct WgIpv4Addr *s, WgIpv4Addr_list l, int i) {
+	WgIpv4Addr_ptr p;
+	p.p = capn_getp(l.p, i, 0);
+	write_WgIpv4Addr(s, p);
+}
+
+WgIpv6Addr_ptr new_WgIpv6Addr(struct capn_segment *s) {
+	WgIpv6Addr_ptr p;
+	p.p = capn_new_struct(s, 8, 1);
+	return p;
+}
+WgIpv6Addr_list new_WgIpv6Addr_list(struct capn_segment *s, int len) {
+	WgIpv6Addr_list p;
+	p.p = capn_new_list(s, len, 8, 1);
+	return p;
+}
+void read_WgIpv6Addr(struct WgIpv6Addr *s capnp_unused, WgIpv6Addr_ptr p) {
+	capn_resolve(&p.p);
+	capnp_use(s);
+	s->addr = capn_get_data(p.p, 0);
+	s->cidr = capn_read8(p.p, 0);
+}
+void write_WgIpv6Addr(const struct WgIpv6Addr *s capnp_unused, WgIpv6Addr_ptr p) {
+	capn_resolve(&p.p);
+	capnp_use(s);
+	capn_setp(p.p, 0, s->addr.p);
+	capn_write8(p.p, 0, s->cidr);
+}
+void get_WgIpv6Addr(struct WgIpv6Addr *s, WgIpv6Addr_list l, int i) {
+	WgIpv6Addr_ptr p;
+	p.p = capn_getp(l.p, i, 0);
+	read_WgIpv6Addr(s, p);
+}
+void set_WgIpv6Addr(const struct WgIpv6Addr *s, WgIpv6Addr_list l, int i) {
+	WgIpv6Addr_ptr p;
+	p.p = capn_getp(l.p, i, 0);
+	write_WgIpv6Addr(s, p);
+}
+
+WgServerSimpleMsg_ptr new_WgServerSimpleMsg(struct capn_segment *s) {
+	WgServerSimpleMsg_ptr p;
+	p.p = capn_new_struct(s, 8, 2);
+	return p;
+}
+WgServerSimpleMsg_list new_WgServerSimpleMsg_list(struct capn_segment *s, int len) {
+	WgServerSimpleMsg_list p;
+	p.p = capn_new_list(s, len, 8, 2);
+	return p;
+}
+void read_WgServerSimpleMsg(struct WgServerSimpleMsg *s capnp_unused, WgServerSimpleMsg_ptr p) {
+	capn_resolve(&p.p);
+	capnp_use(s);
+	s->leasedIpv4.p = capn_getp(p.p, 0, 0);
+	s->leaseTimeout = capn_read32(p.p, 0);
+	s->ipv4Routes.p = capn_getp(p.p, 1, 0);
+}
+void write_WgServerSimpleMsg(const struct WgServerSimpleMsg *s capnp_unused, WgServerSimpleMsg_ptr p) {
+	capn_resolve(&p.p);
+	capnp_use(s);
+	capn_setp(p.p, 0, s->leasedIpv4.p);
+	capn_write32(p.p, 0, s->leaseTimeout);
+	capn_setp(p.p, 1, s->ipv4Routes.p);
+}
+void get_WgServerSimpleMsg(struct WgServerSimpleMsg *s, WgServerSimpleMsg_list l, int i) {
+	WgServerSimpleMsg_ptr p;
+	p.p = capn_getp(l.p, i, 0);
+	read_WgServerSimpleMsg(s, p);
+}
+void set_WgServerSimpleMsg(const struct WgServerSimpleMsg *s, WgServerSimpleMsg_list l, int i) {
+	WgServerSimpleMsg_ptr p;
+	p.p = capn_getp(l.p, i, 0);
+	write_WgServerSimpleMsg(s, p);
+}
diff --git a/protocol.capnp.h b/protocol.capnp.h
new file mode 100644
index 0000000..bf8a949
--- /dev/null
+++ b/protocol.capnp.h
@@ -0,0 +1,119 @@
+#ifndef CAPN_ED77208FB3340CC1
+#define CAPN_ED77208FB3340CC1
+/* AUTO GENERATED - DO NOT EDIT */
+#include <capnp_c.h>
+
+#if CAPN_VERSION != 1
+#error "version mismatch between capnp_c.h and generated code"
+#endif
+
+#ifndef capnp_nowarn
+# ifdef __GNUC__
+#  define capnp_nowarn __extension__
+# else
+#  define capnp_nowarn
+# endif
+#endif
+
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+struct WgClientMsg;
+struct WgIpv4Addr;
+struct WgIpv6Addr;
+struct WgServerSimpleMsg;
+
+typedef struct {capn_ptr p;} WgClientMsg_ptr;
+typedef struct {capn_ptr p;} WgIpv4Addr_ptr;
+typedef struct {capn_ptr p;} WgIpv6Addr_ptr;
+typedef struct {capn_ptr p;} WgServerSimpleMsg_ptr;
+
+typedef struct {capn_ptr p;} WgClientMsg_list;
+typedef struct {capn_ptr p;} WgIpv4Addr_list;
+typedef struct {capn_ptr p;} WgIpv6Addr_list;
+typedef struct {capn_ptr p;} WgServerSimpleMsg_list;
+
+enum WgClientMsg_WgClientRequestType {
+	WgClientMsg_WgClientRequestType_simple = 0
+};
+
+struct WgClientMsg {
+	enum WgClientMsg_WgClientRequestType request;
+};
+
+static const size_t WgClientMsg_word_count = 1;
+
+static const size_t WgClientMsg_pointer_count = 0;
+
+static const size_t WgClientMsg_struct_bytes_count = 8;
+
+struct WgIpv4Addr {
+	uint32_t addr;
+	uint8_t cidr;
+};
+
+static const size_t WgIpv4Addr_word_count = 1;
+
+static const size_t WgIpv4Addr_pointer_count = 0;
+
+static const size_t WgIpv4Addr_struct_bytes_count = 8;
+
+struct WgIpv6Addr {
+	capn_data addr;
+	uint8_t cidr;
+};
+
+static const size_t WgIpv6Addr_word_count = 1;
+
+static const size_t WgIpv6Addr_pointer_count = 1;
+
+static const size_t WgIpv6Addr_struct_bytes_count = 16;
+
+struct WgServerSimpleMsg {
+	WgIpv4Addr_ptr leasedIpv4;
+	uint32_t leaseTimeout;
+	WgIpv4Addr_list ipv4Routes;
+};
+
+static const size_t WgServerSimpleMsg_word_count = 1;
+
+static const size_t WgServerSimpleMsg_pointer_count = 2;
+
+static const size_t WgServerSimpleMsg_struct_bytes_count = 24;
+
+WgClientMsg_ptr new_WgClientMsg(struct capn_segment*);
+WgIpv4Addr_ptr new_WgIpv4Addr(struct capn_segment*);
+WgIpv6Addr_ptr new_WgIpv6Addr(struct capn_segment*);
+WgServerSimpleMsg_ptr new_WgServerSimpleMsg(struct capn_segment*);
+
+WgClientMsg_list new_WgClientMsg_list(struct capn_segment*, int len);
+WgIpv4Addr_list new_WgIpv4Addr_list(struct capn_segment*, int len);
+WgIpv6Addr_list new_WgIpv6Addr_list(struct capn_segment*, int len);
+WgServerSimpleMsg_list new_WgServerSimpleMsg_list(struct capn_segment*, int len);
+
+void read_WgClientMsg(struct WgClientMsg*, WgClientMsg_ptr);
+void read_WgIpv4Addr(struct WgIpv4Addr*, WgIpv4Addr_ptr);
+void read_WgIpv6Addr(struct WgIpv6Addr*, WgIpv6Addr_ptr);
+void read_WgServerSimpleMsg(struct WgServerSimpleMsg*, WgServerSimpleMsg_ptr);
+
+void write_WgClientMsg(const struct WgClientMsg*, WgClientMsg_ptr);
+void write_WgIpv4Addr(const struct WgIpv4Addr*, WgIpv4Addr_ptr);
+void write_WgIpv6Addr(const struct WgIpv6Addr*, WgIpv6Addr_ptr);
+void write_WgServerSimpleMsg(const struct WgServerSimpleMsg*, WgServerSimpleMsg_ptr);
+
+void get_WgClientMsg(struct WgClientMsg*, WgClientMsg_list, int i);
+void get_WgIpv4Addr(struct WgIpv4Addr*, WgIpv4Addr_list, int i);
+void get_WgIpv6Addr(struct WgIpv6Addr*, WgIpv6Addr_list, int i);
+void get_WgServerSimpleMsg(struct WgServerSimpleMsg*, WgServerSimpleMsg_list, int i);
+
+void set_WgClientMsg(const struct WgClientMsg*, WgClientMsg_list, int i);
+void set_WgIpv4Addr(const struct WgIpv4Addr*, WgIpv4Addr_list, int i);
+void set_WgIpv6Addr(const struct WgIpv6Addr*, WgIpv6Addr_list, int i);
+void set_WgServerSimpleMsg(const struct WgServerSimpleMsg*, WgServerSimpleMsg_list, int i);
+
+#ifdef __cplusplus
+}
+#endif
+#endif
diff --git a/protocol.h b/protocol.h
index 47199cd..ff6c04d 100644
--- a/protocol.h
+++ b/protocol.h
@@ -3,7 +3,10 @@
  * Copyright (C) 2018 Wireguard LLC
  */
 
-#ifndef NEGOTIATION_H
-#define NEGOTIATION_H
+#ifndef PROTOCOL_H
+#define PROTOCOL_H
+
+#define WG_DYNAMIC_SERVER_IP "::1"
+#define WG_DYNAMIC_SERVER_PORT 51820
 
 #endif
diff --git a/server.c b/server.c
index 0315ccb..318dc60 100644
--- a/server.c
+++ b/server.c
@@ -3,8 +3,83 @@
  * Copyright (C) 2018 Wireguard LLC
  */
 
-int setup_server(const char interface[])
+#include <stdlib.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <errno.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <sys/socket.h>
+#include <arpa/inet.h>
+#include "wireguard.h"
+#include "protocol.h"
+#include "server.h"
+
+bool is_wg_up_on_iface(const char iface[])
+{
+	wg_device *device;
+	if (wg_get_device(&device, iface) < 0) {
+		return false;
+	} else {
+		return true;
+	}
+}
+
+int setup_server()
+{
+	int sock = -1;
+	int reuseaddr = 1;
+	int ret;
+	struct sockaddr_in6 addr;
+
+	sock = socket(AF_INET6, SOCK_STREAM, 0);
+	if (sock < 0) {
+		return -errno;
+	}
+	setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &reuseaddr,
+		   sizeof(reuseaddr));
+	addr.sin6_family = AF_INET6;
+	addr.sin6_port = htons(WG_DYNAMIC_SERVER_PORT);
+	inet_pton(AF_INET6, WG_DYNAMIC_SERVER_IP, &addr.sin6_addr);
+	ret = bind(sock, (struct sockaddr *)&addr, sizeof(addr));
+	if (ret < 0) {
+		return -errno;
+	}
+	ret = listen(sock, 5);
+	if (ret < 0) {
+		return -errno;
+	}
+	return sock;
+}
+
+static void handle_connection(int conn, struct sockaddr_in6 addr)
 {
 	/* TODO */
-	return -1;
+}
+
+int handle_connections(int sock)
+{
+	int conn = -1;
+	pid_t pid = -1;
+	struct sockaddr_in6 addr;
+	socklen_t addr_size = sizeof(addr);
+	;
+	while (1) {
+		conn = accept(sock, (struct sockaddr *)&addr, &addr_size);
+		if (conn < 0) {
+			return -errno;
+		}
+		pid = fork();
+		if (pid < 0) {
+			return -errno;
+		} else if (pid == 0) {
+			close(sock);
+			handle_connection(conn, addr);
+			close(conn);
+			exit(EXIT_SUCCESS);
+		} else {
+			close(conn);
+		}
+	}
+	return 0;
 }
diff --git a/server.h b/server.h
index 3ffa9c5..43f8af2 100644
--- a/server.h
+++ b/server.h
@@ -6,6 +6,10 @@
 #ifndef SERVER_H
 #define SERVER_H
 
-int setup_server(const char interface[]);
+#include <stdbool.h>
+
+bool is_wg_up_on_iface(const char iface[]);
+int setup_server();
+int handle_connections(int sock);
 
 #endif
diff --git a/wg_dynamic_client.c b/wg_dynamic_client.c
index 318714d..7862e9e 100644
--- a/wg_dynamic_client.c
+++ b/wg_dynamic_client.c
@@ -7,6 +7,7 @@
 
 #include <stdlib.h>
 #include <stdio.h>
+#include <string.h>
 
 const char *PROG_NAME;
 
@@ -17,6 +18,9 @@ static void show_usage()
 
 int main(int argc, char *argv[])
 {
+	const char *iface;
+	int sock;
+
 	PROG_NAME = argv[0];
 
 	if (argc == 1) {
@@ -24,8 +28,22 @@ int main(int argc, char *argv[])
 		return EXIT_FAILURE;
 	}
 
-	if (connect_to_server(argv[1]) < 0) {
-		perror("error connecting to server");
+	iface = argv[1];
+
+	if (!is_server_in_allowed_ips(iface)) {
+		fprintf(stderr, "server is not in allowed IPs for tunnel %s\n",
+			iface);
+		return EXIT_FAILURE;
+	}
+
+	if ((sock = connect_to_server(argv[1])) < 0) {
+		fprintf(stderr, "error connecting to server: %s\n",
+			strerror(-sock));
+		return EXIT_FAILURE;
+	}
+
+	if ((sock = close_connection(sock)) < 0) {
+		fprintf(stderr, "error closing socket: %s\n", strerror(-sock));
 		return EXIT_FAILURE;
 	}
 
diff --git a/wg_dynamic_server.c b/wg_dynamic_server.c
index 191da67..75bf3af 100644
--- a/wg_dynamic_server.c
+++ b/wg_dynamic_server.c
@@ -7,6 +7,7 @@
 
 #include <stdlib.h>
 #include <stdio.h>
+#include <string.h>
 
 const char *PROG_NAME;
 
@@ -17,6 +18,10 @@ static void show_usage()
 
 int main(int argc, char *argv[])
 {
+	const char *iface;
+	int sock;
+	int ret;
+
 	PROG_NAME = argv[0];
 
 	if (argc == 1) {
@@ -24,10 +29,25 @@ int main(int argc, char *argv[])
 		return EXIT_FAILURE;
 	}
 
-    if (setup_server(argv[1]) < 0) {
-        perror("error setting up server");
-        return EXIT_FAILURE;
-    }
+	iface = argv[1];
+
+	if (!is_wg_up_on_iface(iface)) {
+		fprintf(stderr, "no such wireguard iface %s\n", iface);
+		return EXIT_FAILURE;
+	}
+
+	if ((sock = setup_server(argv[1])) < 0) {
+		fprintf(stderr, "error setting up server: %s\n",
+			strerror(-sock));
+		return EXIT_FAILURE;
+	}
+
+	if ((ret = handle_connections(sock)) < 0) {
+		fprintf(stderr, "error while handling connections: %s\n",
+			strerror(-ret));
+		return EXIT_FAILURE;
+	}
 
-	return EXIT_SUCCESS;
+	/* unreachable */
+	return EXIT_FAILURE;
 }
diff --git a/wireguard.c b/wireguard.c
new file mode 120000
index 0000000..172545a
--- /dev/null
+++ b/wireguard.c
@@ -0,0 +1 @@
+WireGuard/contrib/examples/embeddable-wg-library/wireguard.c
\ No newline at end of file
diff --git a/wireguard.h b/wireguard.h
new file mode 120000
index 0000000..7bf9982
--- /dev/null
+++ b/wireguard.h
@@ -0,0 +1 @@
+WireGuard/contrib/examples/embeddable-wg-library/wireguard.h
\ No newline at end of file