From 35aabe675d1ac734652ef9e40d7f84d62809572c Mon Sep 17 00:00:00 2001
From: Alexander Zhylin <zheiling@hotmail.com>
Date: Fri, 29 May 2026 15:38:11 +0300
Subject: [PATCH] uses preadv2() to listen cancel messages from the client.

---
 src/file_p.c  | 15 +++++++++------
 src/session.c |  7 +------
 src/session.h |  3 ++-
 3 files changed, 12 insertions(+), 13 deletions(-)

diff --git a/src/file_p.c b/src/file_p.c
index a3179aa..4796c43 100644
--- a/src/file_p.c
+++ b/src/file_p.c
@@ -23,6 +23,7 @@
 #include <sys/statvfs.h>
 #include <sys/syslog.h>
 #include <sys/types.h>
+#include <sys/uio.h>
 #include <sys/un.h>
 #include <unistd.h>
 
@@ -293,21 +294,23 @@ void file_download(session *sess) {
   int source_d = sess->fd;
   int dest_d = sess->sd;
   char buf[INBUFSIZE];
-  int rlen = read(sess->sd, buf, INBUFSIZE);
-  if (rlen > 0) {
+  struct iovec iov = {.iov_base = buf, .iov_len = INBUFSIZE};
+  /* uses GNU library */
+  ssize_t ret = preadv2(sess->fd, &iov, 1, 0, RWF_NOWAIT);
+  if (ret > 0) {
     char *line;
-    query_extract_from_buf_2(buf, &rlen, &line);
+    query_extract_from_buf_2(buf, &ret, &line);
     if (!strcmp(line, "cancel\n")) {
       free(line);
       /* replace session buffer with the rest of the local buffer */
-      memcpy(sess->buf, buf, rlen);
-      sess->buf_used = rlen;
+      memcpy(sess->buf, buf, ret);
+      sess->buf_used = ret;
       clear_file_from_sess(sess);
       sess->state = OP_WAIT;
       return;
     }
   }
-  rlen = read(source_d, buf, INBUFSIZE);
+  int rlen = read(source_d, buf, INBUFSIZE);
   if (rlen == 0) {
     if (sess->file->rest) {
       print_log(stdout, pl_error, "Error downloading file %s!\n",
diff --git a/src/session.c b/src/session.c
index c8ca2d1..d715f34 100644
--- a/src/session.c
+++ b/src/session.c
@@ -31,11 +31,6 @@ int32_t accept_client(int ls, session *connections[], char *wm) {
     perror("accept");
     return -1;
   }
-  /* set non-blocking behaviour */
-  int flags = fcntl(sd, F_GETFL, 0);
-  flags = flags | O_NONBLOCK;
-  fcntl(sd, F_SETFL, flags);
-  
   session *sess = make_new_session(sd, &addr, wm);
   print_log(stdout, pl_info, "New connection: %s:%u\n",
             inet_ntoa(addr.sin_addr), ntohs(addr.sin_port));
@@ -140,7 +135,7 @@ int query_extract_from_buf(session *sess, char **output_line) {
   return pos + 1;
 }
 
-int query_extract_from_buf_2(char *buf, int *buf_used, char **output_line) {
+int query_extract_from_buf_2(char *buf, ssize_t *buf_used, char **output_line) {
   char *line;
   int pos = -1;
   int _buf_used = *buf_used;
diff --git a/src/session.h b/src/session.h
index 577c12b..a8e607c 100644
--- a/src/session.h
+++ b/src/session.h
@@ -4,13 +4,14 @@
 #ifndef SESSION_H
 #define SESSION_H
 #include "main.h"
+#include <stdio.h>
 int accept_client(int ls, session *connections[], char *wm);
 void session_send_string(struct session *sess, const char *str, ...);
 int query_extract_from_buf(session *sess, char **output_line);
 int session_do_read(session *sess, char **read_str);
 void perform_session_action(session *sess, char *line, server_data_t *s_d);
 void close_session(session *connections[], int sd);
-int query_extract_from_buf_2(char *buf, int *buf_used, char **output_line);
+int query_extract_from_buf_2(char *buf, ssize_t *buf_used, char **output_line);
 /* session *make_new_session(int fd, struct sockaddr_in *from, char *wm); */
 /* int query_extract_from_sess(session *sess, char **output_line); */
 #endif
\ No newline at end of file