diff --git a/.gitignore b/.gitignore
index 3a3cff5b..88181568 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 .vscode
-ciadpi.exe
\ No newline at end of file
+ciadpi*
+*.o
diff --git a/Makefile b/Makefile
index 40f67083..4d96fe86 100644
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,6 @@
 TARGET = ciadpi
 
-CPPFLAGS = -D_XOPEN_SOURCE=500
+#CPPFLAGS = -D_XOPEN_SOURCE=500
 CFLAGS += -I. -std=c99 -Wall -Wno-unused -O2
 WIN_LDFLAGS = -lws2_32 -lmswsock
 
diff --git a/desync.c b/desync.c
index 1b0fbb99..8cbeabc0 100644
--- a/desync.c
+++ b/desync.c
@@ -10,14 +10,16 @@
     #include <sys/socket.h>
     #include <arpa/inet.h>
     #include <netinet/tcp.h>
-    
-    #ifdef __linux__
+
     #include <sys/mman.h>
-    #include <sys/sendfile.h>
+    #ifdef __linux__
+        #include <sys/sendfile.h>
+    #endif
     #include <fcntl.h>
 
-    #include <desync.h>
-    
+    #include "desync.h"
+
+    #ifdef __linux__
     #ifdef MFD_CLOEXEC
         #include <sys/syscall.h>
         #define memfd_create(name, flags) syscall(__NR_memfd_create, name, flags);
@@ -82,7 +84,7 @@ static inline void delay(long ms)
 #define delay(ms) Sleep(ms)
 #endif
 
-#ifdef __linux__
+#if defined(__linux__) || defined(__FreeBSD__)
 void wait_send(int sfd)
 {
     for (int i = 0; params.wait_send && i < 500; i++) {
@@ -118,7 +120,7 @@ void wait_send(int sfd)
 #define wait_send_if_support(sfd) // :(
 #endif
 
-#ifdef __linux__
+#if defined(__linux__) || defined(__FreeBSD__)
 ssize_t send_fake(int sfd, char *buffer,
         int cnt, long pos, int fa, struct desync_params *opt)
 {
@@ -165,11 +167,18 @@ ssize_t send_fake(int sfd, char *buffer,
             break;
         }
         if (opt->md5sig) {
+#ifdef __linux__
             struct tcp_md5sig md5 = {
                 .tcpm_keylen = 5
             };
             memcpy(&md5.tcpm_addr, &addr, addr_size);
-            
+#elif defined(__FreeBSD__)
+            // FIXME: Should be struct tcpmd5_support
+            // but netipsec/ipsec_support.h hides this under ifdef KERNEL
+            int md5 = 1;
+#else
+#error
+#endif
             if (setsockopt(sfd, IPPROTO_TCP,
                     TCP_MD5SIG, (char *)&md5, sizeof(md5)) < 0) {
                 uniperror("setsockopt TCP_MD5SIG");
@@ -183,7 +192,11 @@ ssize_t send_fake(int sfd, char *buffer,
             break;
         }
         
+#ifdef __linux__
         len = sendfile(sfd, ffd, 0, pos);
+#else
+        len = sendfile(sfd, ffd, 0, pos, NULL, NULL, 0);
+#endif
         if (len < 0) {
             uniperror("sendfile");
             break;
@@ -201,10 +214,16 @@ ssize_t send_fake(int sfd, char *buffer,
             break;
         }
         if (opt->md5sig) {
+#ifdef __linux__
             struct tcp_md5sig md5 = {
                 .tcpm_keylen = 0
             };
             memcpy(&md5.tcpm_addr, &addr, addr_size);
+#elif defined(__FreeBSD__)
+            int md5 = 0;
+#else
+#error
+#endif
             
             if (setsockopt(sfd, IPPROTO_TCP,
                     TCP_MD5SIG, (char *)&md5, sizeof(md5)) < 0) {
diff --git a/extend.c b/extend.c
index b91edf12..247010d4 100644
--- a/extend.c
+++ b/extend.c
@@ -30,15 +30,16 @@ int set_timeout(int fd, unsigned int s)
         uniperror("setsockopt TCP_USER_TIMEOUT");
         return -1;
     }
-    #else
-    #ifdef _WIN32
+    #elif defined(__FreeBSD__)
+    // https://wiki.freebsd.org/CatalinNicutar/TCPUTO
+    // sadly not yet available
+    #elif defined(_WIN32)
     if (setsockopt(fd, IPPROTO_TCP,
             TCP_MAXRT, (char *)&s, sizeof(s))) {
         uniperror("setsockopt TCP_MAXRT");
         return -1;
     }
     #endif
-    #endif
     return 0;
 }
 
diff --git a/main.c b/main.c
index 19e0c2b3..be92616b 100644
--- a/main.c
+++ b/main.c
@@ -24,6 +24,10 @@
     #define close(fd) closesocket(fd)
 #endif
 
+#ifdef __FreeBSD__
+    #include <netinet/in.h>
+#endif
+
 #define VERSION "12"
 
 char oob_char[1] = "a";
@@ -57,7 +61,7 @@ struct params params = {
         .sin6_family = AF_INET6
     },
     .laddr = {
-        .sin6_family = AF_INET
+        .sin6_family = AF_INET6
     },
     .debug = 0
 };
@@ -94,7 +98,7 @@ const char help_text[] = {
     #ifdef FAKE_SUPPORT
     "    -f, --fake <n[+s]>        Split and send fake packet\n"
     "    -t, --ttl <num>           TTL of fake packets, default 8\n"
-    #ifdef __linux__
+    #if defined(__linux__) || defined(__FreeBSD__)
     "    -k, --ip-opt[=f|:str]     IP options of fake packets\n"
     "    -S, --md5sig              Add MD5 Signature option for fake packets\n"
     #endif
@@ -138,7 +142,7 @@ const struct option options[] = {
     #ifdef FAKE_SUPPORT
     {"fake",          1, 0, 'f'},
     {"ttl",           1, 0, 't'},
-    #ifdef __linux__
+    #if defined(__linux__) || defined(__FreeBSD__)
     {"ip-opt",        2, 0, 'k'},
     {"md5sig",        0, 0, 'S'},
     #endif
diff --git a/packets.c b/packets.c
index 540ba86b..100f3c69 100644
--- a/packets.c
+++ b/packets.c
@@ -1,6 +1,10 @@
-#define _GNU_SOURCE
+#ifdef __FreeBSD__
+    #include <strings.h>
+#else
+    #define _GNU_SOURCE
+#endif
 
-#include <packets.h>
+#include "packets.h"
 #include <ctype.h>
 #include <stdio.h>
 #include <stdlib.h>
diff --git a/params.h b/params.h
index 825950c3..79047d62 100644
--- a/params.h
+++ b/params.h
@@ -1,5 +1,6 @@
 #include <stdint.h>
 #include <stdio.h>
+#include <unistd.h>
 
 #include "mpool.h"
 
@@ -9,7 +10,11 @@
     #include <arpa/inet.h>
 #endif
 
-#if defined(__linux__) || defined(_WIN32)
+#ifdef __FreeBSD__
+    #include <netinet/in.h>
+#endif
+
+#if defined(__linux__) || defined(_WIN32) || defined(__FreeBSD__)
 #define FAKE_SUPPORT 1
 #define TIMEOUT_SUPPORT 1
 #endif
@@ -107,4 +112,4 @@ extern struct packet fake_http;
 extern struct packet oob_data;
 extern struct packet fake_udp;
 
-extern char ip_option[1];
\ No newline at end of file
+extern char ip_option[1];
diff --git a/proxy.c b/proxy.c
index de5ad7ad..e3151d60 100644
--- a/proxy.c
+++ b/proxy.c
@@ -80,7 +80,7 @@ static inline char addr_equ(
 
 static inline int nb_socket(int domain, int type)
 {
-    #ifdef __linux__
+    #if defined(__linux__) || defined(__FreeBSD__)
     int fd = socket(domain, type | SOCK_NONBLOCK, 0);
     #else
     int fd = socket(domain, type, 0);
@@ -96,15 +96,13 @@ static inline int nb_socket(int domain, int type)
         close(fd);
         return -1;
     }
-    #else
-    #ifndef __linux__
+    #elif !defined(__linux__)
     if (fcntl(fd, F_SETFL, O_NONBLOCK) < 0) {
         uniperror("fcntl");
         close(fd);
         return -1;
     }
     #endif
-    #endif
     return fd;
 }
 
@@ -515,7 +513,7 @@ static inline int on_accept(struct poolhd *pool, struct eval *val)
     
     while (1) {
         socklen_t len = sizeof(client);
-        #ifdef __linux__
+        #if defined(__linux__) || defined(__FreeBSD__)
         int c = accept4(val->fd, &client.sa, &len, SOCK_NONBLOCK);
         #else
         int c = accept(val->fd, &client.sa, &len);
diff --git a/proxy.h b/proxy.h
index b9db0a86..8da072b4 100644
--- a/proxy.h
+++ b/proxy.h
@@ -4,6 +4,7 @@
     #include <ws2tcpip.h>
 #else
     #include <arpa/inet.h>
+    #include <sys/socket.h>
 #endif
 
 #include "conev.h"