1 files changed, 63 insertions, 0 deletions
diff --git a/internal/namespace/launcher_src/launcher.c b/internal/namespace/launcher_src/launcher.c
index 7bbbce7..60c6558 100644
--- a/internal/namespace/launcher_src/launcher.c
+++ b/internal/namespace/launcher_src/launcher.c
@@ -13,6 +13,69 @@ int main(int argc, char **argv) {
         return 1;
     }
 
+    // Check if we are joining an existing namespace
+    char *join_pid_str = getenv("WG_WRAP_JOIN_PID");
+    if (join_pid_str != NULL && strlen(join_pid_str) > 0) {
+        int target_pid = atoi(join_pid_str);
+        if (target_pid > 0) {
+            char path[128];
+            int fd;
+
+            // 1. Join User Namespace first
+            snprintf(path, sizeof(path), "/proc/%d/ns/user", target_pid);
+            fd = open(path, O_RDONLY);
+            if (fd == -1) {
+                perror("open target user namespace");
+                return 1;
+            }
+            if (setns(fd, CLONE_NEWUSER) == -1) {
+                perror("setns CLONE_NEWUSER");
+                close(fd);
+                return 1;
+            }
+            close(fd);
+
+            // 2. Join Mount Namespace
+            snprintf(path, sizeof(path), "/proc/%d/ns/mnt", target_pid);
+            fd = open(path, O_RDONLY);
+            if (fd == -1) {
+                perror("open target mount namespace");
+                return 1;
+            }
+            if (setns(fd, CLONE_NEWNS) == -1) {
+                perror("setns CLONE_NEWNS");
+                close(fd);
+                return 1;
+            }
+            close(fd);
+
+            // 3. Join Network Namespace
+            snprintf(path, sizeof(path), "/proc/%d/ns/net", target_pid);
+            fd = open(path, O_RDONLY);
+            if (fd == -1) {
+                perror("open target network namespace");
+                return 1;
+            }
+            if (setns(fd, CLONE_NEWNET) == -1) {
+                perror("setns CLONE_NEWNET");
+                close(fd);
+                return 1;
+            }
+            close(fd);
+
+            // Execute the target command
+            if (argv[0] == NULL) {
+                fprintf(stderr, "No target binary provided in argv[0]\n");
+                return 1;
+            }
+            if (execv(argv[0], argv) == -1) {
+                perror("execv failed");
+                return 1;
+            }
+            return 0;
+        }
+    }
+
     // 1. Capture host identities BEFORE unsharing
     uid_t current_uid = getuid();
     gid_t current_gid = getgid();