From 076da4264b4c8ec379a4e81c6a427b4425c6f7ba Mon Sep 17 00:00:00 2001
From: Evgeny <me@jeka.su>
Date: Wed, 4 Feb 2026 22:35:40 +0300
Subject: [PATCH] Fix: ACK section length calculation and increase socket
 buffers

---
 src/etcp.c             | 29 +++++++++++++++--------------
 src/etcp_connections.c | 12 +++++++++++-
 2 files changed, 26 insertions(+), 15 deletions(-)

diff --git a/src/etcp.c b/src/etcp.c
index 82b49c47..071ba564 100644
--- a/src/etcp.c
+++ b/src/etcp.c
@@ -744,20 +744,21 @@ void etcp_conn_input(struct ETCP_DGRAM* pkt) {
 
         // Process sections as per protocol.txt
         switch (type) {
-            case ETCP_SECTION_ACK: {
-                int elm_cnt=data[1];
-                uint32_t till=data[2] | (data[3]<<8) | (data[4]<<16) | (data[5]<<24);
-                data+=6;
-                for (int i=0; i<elm_cnt; i++) {
-                    uint32_t seq=data[0] | (data[1]<<8) | (data[2]<<16) | (data[3]<<24);
-                    uint16_t ts=data[4] | (data[5]<<8);
-                    uint16_t dts=data[6] | (data[7]<<8);
-                    etcp_ack_recv(etcp, seq, ts, dts);
-                    data+=8;
-                    }
-                while (etcp->rx_ack_till-till<0) { etcp->rx_ack_till++; etcp_ack_recv(etcp, etcp->rx_ack_till, -1, -1); }// подтверждаем всё по till
-                break;
-            }
+            case ETCP_SECTION_ACK: {
+                int elm_cnt=data[1];
+                uint32_t till=data[2] | (data[3]<<8) | (data[4]<<16) | (data[5]<<24);
+                int ack_section_len = 6 + elm_cnt * 8;
+                data+=ack_section_len;
+                len-=ack_section_len;
+                for (int i=0; i<elm_cnt; i++) {
+                    uint32_t seq=data[-ack_section_len+6+i*8] | (data[-ack_section_len+7+i*8]<<8) | (data[-ack_section_len+8+i*8]<<16) | (data[-ack_section_len+9+i*8]<<24);
+                    uint16_t ts=data[-ack_section_len+10+i*8] | (data[-ack_section_len+11+i*8]<<8);
+                    uint16_t dts=data[-ack_section_len+12+i*8] | (data[-ack_section_len+13+i*8]<<8);
+                    etcp_ack_recv(etcp, seq, ts, dts);
+                    }
+                while ((int32_t)(etcp->rx_ack_till-till)<0) { etcp->rx_ack_till++; etcp_ack_recv(etcp, etcp->rx_ack_till, -1, -1); }// подтверждаем всё по till
+                break;
+            }
             case ETCP_SECTION_PAYLOAD: {
 
                 if (len>=5) {
diff --git a/src/etcp_connections.c b/src/etcp_connections.c
index cb400e64..c9ec09dc 100644
--- a/src/etcp_connections.c
+++ b/src/etcp_connections.c
@@ -274,7 +274,17 @@ struct ETCP_SOCKET* etcp_socket_add(struct UTUN_INSTANCE* instance, struct socka
     if (setsockopt(e_sock->fd, SOL_SOCKET, SO_REUSEADDR, &reuse, sizeof(reuse)) < 0) {
         DEBUG_WARN(DEBUG_CATEGORY_CONNECTION, "Failed to set SO_REUSEADDR: %s", strerror(errno));
     }
-    
+
+    // Increase socket buffers for high throughput
+    int sndbuf = 4 * 1024 * 1024;  // 4MB send buffer
+    int rcvbuf = 4 * 1024 * 1024;  // 4MB receive buffer
+    if (setsockopt(e_sock->fd, SOL_SOCKET, SO_SNDBUF, &sndbuf, sizeof(sndbuf)) < 0) {
+        DEBUG_WARN(DEBUG_CATEGORY_CONNECTION, "Failed to set SO_SNDBUF: %s", strerror(errno));
+    }
+    if (setsockopt(e_sock->fd, SOL_SOCKET, SO_RCVBUF, &rcvbuf, sizeof(rcvbuf)) < 0) {
+        DEBUG_WARN(DEBUG_CATEGORY_CONNECTION, "Failed to set SO_RCVBUF: %s", strerror(errno));
+    }
+
     int flags = fcntl(e_sock->fd, F_GETFL, 0);
     fcntl(e_sock->fd, F_SETFL, flags | O_NONBLOCK);