From 550f2d2f5f9b5d454a9798e2d8b50a0fb821c7ad Mon Sep 17 00:00:00 2001
From: ruti <>
Date: Fri, 9 Aug 2024 22:49:44 +0300
Subject: [PATCH] drop-sack

---
 desync.c | 53 +++++++++++++++++++++++++++++++++++++++++++++++++++--
 desync.h |  2 ++
 extend.c |  4 ++++
 main.c   |  8 ++++++++
 params.h |  1 +
 5 files changed, 66 insertions(+), 2 deletions(-)

diff --git a/desync.c b/desync.c
index b46f137..d305d86 100644
--- a/desync.c
+++ b/desync.c
@@ -14,9 +14,10 @@
     
     #ifndef __linux__
     #include <netinet/tcp.h>
-    #else    
-    #include <sys/sendfile.h>
+    #else
     #include <linux/tcp.h>
+    #include <sys/sendfile.h>
+    #include <linux/filter.h>
     #include <sys/syscall.h>
     
     #define memfd_create(name, flags) syscall(__NR_memfd_create, name, flags)
@@ -67,6 +68,32 @@ int setttl(int fd, int ttl, int family) {
     return 0;
 }
 
+#ifdef __linux__
+int drop_sack(int fd)
+{
+    struct sock_filter code[] = {
+        { 0x30, 0, 0, 0x0000000c },
+        { 0x74, 0, 0, 0x00000004 },
+        { 0x35, 0, 3, 0x0000000b },
+        { 0x30, 0, 0, 0x00000022 },
+        { 0x15, 0, 1, 0x00000005 },
+        { 0x6,  0, 0, 0x00000000 },
+        { 0x6,  0, 0, 0x00040000 },
+    };
+    struct sock_fprog bpf = {
+        .len = sizeof(code)/sizeof(*code),
+        .filter = code
+    };
+    if (setsockopt(fd, SOL_SOCKET, 
+            SO_ATTACH_FILTER, (char *)&bpf, sizeof(bpf)) == -1) {
+        uniperror("setsockopt SO_ATTACH_FILTER");
+        return -1;
+    }
+    return 0;
+}
+#endif
+
+
 #ifndef _WIN32
 static inline void delay(long ms)
 {
@@ -471,6 +498,11 @@ ssize_t desync(int sfd, char *buffer, size_t bfsize,
         }
     }
     // desync
+    #ifdef __linux__
+    if (dp.drop_sack && drop_sack(sfd)) {
+        return -1;
+    }
+    #endif
     long lp = offset;
     
     for (int i = 0; i < dp.parts_n; i++) {
@@ -565,6 +597,23 @@ ssize_t desync(int sfd, char *buffer, size_t bfsize,
 }
 
 
+int post_desync(int sfd, int dp_c)
+{
+    struct desync_params *dp = &params.dp[dp_c];
+    
+    #ifdef __linux__
+    if (dp->drop_sack) {
+        if (setsockopt(sfd, SOL_SOCKET, 
+                SO_DETACH_FILTER, &dp_c, sizeof(dp_c)) == -1) {
+            uniperror("setsockopt SO_DETACH_FILTER");
+            return -1;
+        }
+    }
+    #endif
+    return 0;
+}
+
+
 ssize_t desync_udp(int sfd, char *buffer, size_t bfsize,
         ssize_t n, struct sockaddr *dst, int dp_c)
 {
diff --git a/desync.h b/desync.h
index a915179..cb0d038 100644
--- a/desync.h
+++ b/desync.h
@@ -18,4 +18,6 @@ int get_family(struct sockaddr *dst);
 
 int setttl(int fd, int ttl, int family);
 
+int post_desync(int sfd, int dp_c);
+
 #endif
diff --git a/extend.c b/extend.c
index 5b71e27..da40589 100644
--- a/extend.c
+++ b/extend.c
@@ -285,6 +285,10 @@ int on_tunnel_check(struct poolhd *pool, struct eval *val,
     }
     int m = pair->attempt;
     
+    if (post_desync(val->fd, m)) {
+        return -1;
+    }
+    
     if (!pair->cache) {
         return 0;
     }
diff --git a/main.c b/main.c
index cb2684b..8a26e3f 100644
--- a/main.c
+++ b/main.c
@@ -106,6 +106,9 @@ const char help_text[] = {
     "    -M, --mod-http <h,d,r>    Modify HTTP: hcsmix,dcsmix,rmspace\n"
     "    -r, --tlsrec <n[+s]>      Make TLS record at position\n"
     "    -a, --udp-fake <count>    UDP fakes count, default 0\n"
+    #ifdef __linux__
+    "    -Y, --drop-sack           Drop packets with SACK extension\n"
+    #endif
 };
 
 
@@ -156,6 +159,7 @@ const struct option options[] = {
     {"delay",         1, 0, 'w'}, //
     {"not-wait-send", 0, 0, 'W'}, //
     #ifdef __linux__
+    {"drop-sack",     0, 0, 'Y'},
     {"protect-path",  1, 0, 'P'}, //
     #endif
     {0}
@@ -802,6 +806,10 @@ int main(int argc, char **argv)
             }
             break;
             
+        case 'Y':
+            dp->drop_sack = 1;
+            break;
+            
         case 'w': //
             params.sfdelay = strtol(optarg, &end, 0);
             if (params.sfdelay < 0 || optarg == end 
diff --git a/params.h b/params.h
index caa9057..173ae1f 100644
--- a/params.h
+++ b/params.h
@@ -67,6 +67,7 @@ struct desync_params {
     struct packet fake_data;
     int udp_fake_count;
     int fake_offset;
+    char drop_sack;
     
     int parts_n;
     struct part *parts;