diff --git a/src/server.c b/src/server.c
index 23c5bb9d..6310084c 100644
--- a/src/server.c
+++ b/src/server.c
@@ -78,6 +78,18 @@
 #define MAX_FRAG 1
 #endif
 
+#ifdef USE_NFCONNTRACK_TOS
+
+#ifndef MARK_MAX_PACKET
+#define MARK_MAX_PACKET 10
+#endif
+
+#ifndef MARK_MASK_PREFIX
+#define MARK_MASK_PREFIX 0xDC00
+#endif
+
+#endif
+
 static void signal_cb(EV_P_ ev_signal *w, int revents);
 static void accept_cb(EV_P_ ev_io *w, int revents);
 static void server_send_cb(EV_P_ ev_io *w, int revents);
@@ -551,6 +563,93 @@ connect_to_remote(EV_P_ struct addrinfo *res,
     return remote;
 }
 
+#ifdef USE_NFCONNTRACK_TOS
+int setMarkDscpCallback(enum nf_conntrack_msg_type type, struct nf_conntrack *ct, void *data)
+{
+	server_t* server = (server_t*) data;
+	struct dscptracker* tracker = server->tracker;
+
+	tracker->mark = nfct_get_attr_u32(ct, ATTR_MARK);
+	if ((tracker->mark & 0xff00) == MARK_MASK_PREFIX) {
+		// Extract DSCP value from mark value
+		tracker->dscp = tracker->mark & 0x00ff;
+		int tos = (tracker->dscp) << 2;
+		if (setsockopt(server->fd, IPPROTO_IP, IP_TOS, &tos, sizeof(tos)) != 0) {
+			ERROR("iptable setsockopt IP_TOS");
+		};
+	}
+	return NFCT_CB_CONTINUE;
+}
+
+void conntrackQuery(server_t* server) {
+	struct dscptracker* tracker = server->tracker;
+	if(tracker && tracker->ct) {
+		// Trying query mark from nf conntrack
+		struct nfct_handle *h = nfct_open(CONNTRACK, 0);
+		if (h) {
+			nfct_callback_register(h, NFCT_T_ALL, setMarkDscpCallback, (void*) server);
+			int x = nfct_query(h, NFCT_Q_GET, tracker->ct);
+			if (x == -1) {
+				LOGE("QOS: Failed to retrieve connection mark %s", strerror(errno));
+			}
+			nfct_close(h);
+		} else {
+			LOGE("QOS: Failed to open conntrack handle for upstream netfilter mark retrieval.");
+		}
+	}
+}
+
+void setTosFromConnmark(remote_t* remote, server_t* server)
+{
+	if(server->tracker && server->tracker->ct) {
+		if(server->tracker->mark == 0 && server->tracker->packet_count < MARK_MAX_PACKET) {
+			server->tracker->packet_count++;
+			conntrackQuery(server);
+		}
+	} else {
+		socklen_t len;
+		struct sockaddr_storage sin;
+		len = sizeof(sin);
+		if (getsockname(remote->fd, (struct sockaddr *)&sin, &len) == 0) {
+			struct sockaddr_storage from_addr;
+			len = sizeof from_addr;
+			if(getpeername(remote->fd, (struct sockaddr*)&from_addr, &len) == 0) {
+				if((server->tracker = (struct dscptracker*) malloc(sizeof(struct dscptracker))))
+				{
+					if ((server->tracker->ct = nfct_new())) {
+						// Build conntrack query SELECT
+						if (from_addr.ss_family == AF_INET) {
+							struct sockaddr_in *src = (struct sockaddr_in *)&from_addr;
+							struct sockaddr_in *dst = (struct sockaddr_in *)&sin;
+
+							nfct_set_attr_u8(server->tracker->ct, ATTR_L3PROTO, AF_INET);
+							nfct_set_attr_u32(server->tracker->ct, ATTR_IPV4_DST, dst->sin_addr.s_addr);
+							nfct_set_attr_u32(server->tracker->ct, ATTR_IPV4_SRC, src->sin_addr.s_addr);
+							nfct_set_attr_u16(server->tracker->ct, ATTR_PORT_DST, dst->sin_port);
+							nfct_set_attr_u16(server->tracker->ct, ATTR_PORT_SRC, src->sin_port);
+						} else if (from_addr.ss_family == AF_INET6) {
+							struct sockaddr_in6 *src = (struct sockaddr_in6 *)&from_addr;
+							struct sockaddr_in6 *dst = (struct sockaddr_in6 *)&sin;
+
+							nfct_set_attr_u8(server->tracker->ct, ATTR_L3PROTO, AF_INET6);
+							nfct_set_attr(server->tracker->ct, ATTR_IPV6_DST, dst->sin6_addr.s6_addr);
+							nfct_set_attr(server->tracker->ct, ATTR_IPV6_SRC, src->sin6_addr.s6_addr);
+							nfct_set_attr_u16(server->tracker->ct, ATTR_PORT_DST, dst->sin6_port);
+							nfct_set_attr_u16(server->tracker->ct, ATTR_PORT_SRC, src->sin6_port);
+						}
+						nfct_set_attr_u8(server->tracker->ct, ATTR_L4PROTO, IPPROTO_TCP);
+						conntrackQuery(server);
+					} else {
+						LOGE("Failed to allocate new conntrack for upstream netfilter mark retrieval.");
+						server->tracker->ct=NULL;
+					};
+				}
+			}
+		}
+	}
+}
+#endif
+
 static void
 server_recv_cb(EV_P_ ev_io *w, int revents)
 {
@@ -1004,6 +1103,9 @@ remote_recv_cb(EV_P_ ev_io *w, int revents)
         return;
     }
 
+#ifdef USE_NFCONNTRACK_TOS
+    setTosFromConnmark(remote, server);
+#endif
     int s = send(server->fd, server->buf->data, server->buf->len, 0);
 
     if (s == -1) {
@@ -1232,6 +1334,17 @@ new_server(int fd, listen_ctx_t *listener)
 static void
 free_server(server_t *server)
 {
+#ifdef USE_NFCONNTRACK_TOS
+    if(server->tracker) {
+        struct dscptracker* tracker = server->tracker;
+        struct nf_conntrack* ct = server->tracker->ct;
+        server->tracker = NULL;
+        if (ct) {
+            nfct_destroy(ct);
+       }
+       free(tracker);
+    };
+#endif
     cork_dllist_remove(&server->entries);
 
     if (server->remote != NULL) {
diff --git a/src/server.h b/src/server.h
index a1d74995..90cf051d 100644
--- a/src/server.h
+++ b/src/server.h
@@ -53,6 +53,20 @@ typedef struct server_ctx {
     struct server *server;
 } server_ctx_t;
 
+#ifdef USE_NFCONNTRACK_TOS
+
+#include <libnetfilter_conntrack/libnetfilter_conntrack.h>
+#include <libnetfilter_conntrack/libnetfilter_conntrack_tcp.h>
+
+struct dscptracker {
+        struct nf_conntrack *ct;
+        long unsigned int mark;
+        unsigned int dscp;
+        unsigned int packet_count;
+};
+
+#endif
+
 typedef struct server {
     int fd;
     int stage;
@@ -70,6 +84,9 @@ typedef struct server {
     struct ResolvQuery *query;
 
     struct cork_dllist_item entries;
+#ifdef USE_NFCONNTRACK_TOS
+    struct dscptracker* tracker;
+#endif
 } server_t;
 
 typedef struct query {