From 90ca5a36c511c9753878408984efa31dd99e9dfa Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Deuc=D0=B5?= <shurd@sasktel.net>
Date: Sat, 10 Apr 2021 16:01:50 -0400
Subject: [PATCH] Finally document socket_check() behaviour.
Tweak the poll() implementation to match.
Should fix #248
---
src/xpdev/sockwrap.c | 42 ++++++++++++++++++++++++++++++++++--------
1 file changed, 34 insertions(+), 8 deletions(-)
diff --git a/src/xpdev/sockwrap.c b/src/xpdev/sockwrap.c
index c6f32f0377..78918c7ccd 100644
--- a/src/xpdev/sockwrap.c
+++ b/src/xpdev/sockwrap.c
@@ -270,6 +270,32 @@ off_t recvfilesocket(int sock, int file, off_t *offset, off_t count)
/* Return true if connected, optionally sets *rd_p to true if read data available */
+/*
+ * The exact conditions where rd_p is set to TRUE and the return value
+ * is true or false are complex, but the intent appears to be as follows:
+ *
+ * If the remote has half-closed the socket, rd_p should be FALSE and
+ * the function should return FALSE.
+ *
+ * If we have half-closed the socket, wr_p should be TRUE and the function
+ * should return TRUE.
+ *
+ * If the socket is completely closed, wr_p should be TRUE, rd_p should be
+ * FALSE, and the function should return FALSE, unless rd_p is NULL in which
+ * case, the function should return TRUE.
+ *
+ * When the function is open in both directions, wr_p will indicate write
+ * buffers are available, rd_p will indicate data is available to be recv()ed
+ * and the return value should be TRUE.
+ *
+ * If the socket is invalid, rd_p should be FALSE, wr_p should be FALSE, and
+ * the function should return FALSE.
+ *
+ * These rules have various exceptions when errors are returned by select(),
+ * poll(), or recv(), which will generally cause a FALSE return with rd_p
+ * being FALSE and wr_p being FALSE if select/poll failed, or indicating
+ * available write buffers otherwise.
+ */
BOOL socket_check(SOCKET sock, BOOL* rd_p, BOOL* wr_p, DWORD timeout)
{
#ifdef PREFER_POLL
@@ -297,12 +323,13 @@ BOOL socket_check(SOCKET sock, BOOL* rd_p, BOOL* wr_p, DWORD timeout)
return TRUE;
if (j == 1) {
- if (wr_p != NULL && (pfd.revents & POLLOUT))
+ if (wr_p != NULL && (pfd.revents & POLLOUT)) {
*wr_p = TRUE;
- if (rd_p != NULL && (pfd.revents & POLLIN))
- *rd_p = TRUE;
+ if (rd_p == NULL)
+ return TRUE;
+ }
- if (pfd.revents & (POLLERR | POLLNVAL))
+ if (pfd.revents & (POLLERR | POLLNVAL | POLLHUP))
return FALSE;
if(pfd.revents & ~(POLLOUT) && (rd_p !=NULL || wr_p==NULL)) {
@@ -310,19 +337,18 @@ BOOL socket_check(SOCKET sock, BOOL* rd_p, BOOL* wr_p, DWORD timeout)
if(rd==1 || (rd==SOCKET_ERROR && ERROR_VALUE==EMSGSIZE)) {
if(rd_p!=NULL)
*rd_p=TRUE;
- return(TRUE);
+ return TRUE;
}
- return FALSE;
}
+ return FALSE;
}
if (j == -1) {
if (errno == EINTR || errno == ENOMEM)
return TRUE;
- return FALSE;
}
- return TRUE;
+ return FALSE;
#else
char ch;
int i,rd;
--
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