From: Stefan Eissing <stefan@eissing.org>
Date: Mon, 16 Jun 2025 10:19:52 +0000 (+0200)
Subject: multi: fix polling with pending input
X-Git-Tag: curl-8_15_0~251
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=62349e45a818e50b5cdcd017c149f9dc87fce9fe;p=thirdparty%2Fcurl.git

multi: fix polling with pending input

When multi creates the pollset of a transfer, it checks now if
a connection (FIRST/SECONDARY) socket waits on POLLIN and has input data
pending in filters (relevant to OpenSSL's new read ahead). If so, it
triggers a timeout on the transfer via EXPIRE_RUN_NOW.

This fixes sporadic stalls in test 988 when running event based.

Closes #17636
---

diff --git a/lib/cfilters.c b/lib/cfilters.c
index 4c83657e87..69cbb68e27 100644
--- a/lib/cfilters.c
+++ b/lib/cfilters.c
@@ -1069,3 +1069,16 @@ void Curl_pollset_check(struct Curl_easy *data,
   }
   *pwant_read = *pwant_write = FALSE;
 }
+
+bool Curl_pollset_want_read(struct Curl_easy *data,
+                            struct easy_pollset *ps,
+                            curl_socket_t sock)
+{
+  unsigned int i;
+  (void)data;
+  for(i = 0; i < ps->num; ++i) {
+    if((ps->sockets[i] == sock) && (ps->actions[i] & CURL_POLL_IN))
+      return TRUE;
+  }
+  return FALSE;
+}
diff --git a/lib/cfilters.h b/lib/cfilters.h
index 4f678f8689..edcbb6f375 100644
--- a/lib/cfilters.h
+++ b/lib/cfilters.h
@@ -620,6 +620,13 @@ void Curl_pollset_check(struct Curl_easy *data,
                         struct easy_pollset *ps, curl_socket_t sock,
                         bool *pwant_read, bool *pwant_write);
 
+/**
+ * Return TRUE if the pollset contains socket with CURL_POLL_IN.
+ */
+bool Curl_pollset_want_read(struct Curl_easy *data,
+                            struct easy_pollset *ps,
+                            curl_socket_t sock);
+
 /**
  * Types and macros used to keep the current easy handle in filter calls,
  * allowing for nested invocations. See #10336.
diff --git a/lib/multi.c b/lib/multi.c
index 51a5fb3f71..ef41650b32 100644
--- a/lib/multi.c
+++ b/lib/multi.c
@@ -1038,6 +1038,18 @@ void Curl_multi_getsock(struct Curl_easy *data,
     break;
   }
 
+
+  /* Waiting to receive with buffered input.
+   * Make transfer run again at next opportunity. */
+  if((Curl_pollset_want_read(data, ps, data->conn->sock[FIRSTSOCKET]) &&
+      Curl_conn_data_pending(data, FIRSTSOCKET)) ||
+     (Curl_pollset_want_read(data, ps, data->conn->sock[SECONDARYSOCKET]) &&
+      Curl_conn_data_pending(data, SECONDARYSOCKET))) {
+    CURL_TRC_M(data, "%s pollset[] has POLLIN, but there is still "
+               "buffered input to consume -> EXPIRE_RUN_NOW", caller);
+    Curl_expire(data, 0, EXPIRE_RUN_NOW);
+  }
+
   switch(ps->num) {
     case 0:
       CURL_TRC_M(data, "%s pollset[], timeouts=%zu, paused %d/%d (r/w)",