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Add an environement variable to control stdio mode

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stdio descriptors (stdin, stdout and stderr) can be operated in various
modes by win32compat code. The behavior is set very early in
fd_table_initialize() by setting pio->type.

In https://github.com/PowerShell/Win32-OpenSSH/issues/1427 it was
chosen to set pio->type to NONSOCK_SYNC_FD to resolve an I/O hang
problem. Unfortunately this introduce problems for other ssh usage.

sshfs-wiun uses ssh and has at leas 6 open issues for the same
problem introduced by this NONSOCK_SYNC_FD change:
https://github.com/winfsp/sshfs-win/issues?q=is%3Aissue+cb+%3A87

The sshfs-win workaround it to use an older ssh.exe from cygwin, which
is bundled with sshfs-win. This program is unable to use ssh-agent,
which is quite frustrating. And if PATH is not set to use it, sshfs-win
cannot work.

This change introduce an OPENSSH_STDIO_MODE environment variable that
can be set to the following values: unknown, sock, nonsock, nonsock_sync.
It cause pio->type to be set to UNKNOWN_FD, SOCK_FD, NONSOCK_FD, and
NONSOCK_SYNC_FD respecitively. The default behavior when the variable
is not set is unchanged (which means NONSOCK_SYNC_FD).

Setting OPENSSH_STDIO_MODE="nonsock" lets sshfs-win work again with
openssh-portable ssh.exe. ssh-agent can be used, and this is good.
This commit is contained in:
Emmanuel Dreyfus 2024-10-31 08:32:20 +01:00
parent a915f06c78
commit a8adf827bd
1 changed files with 16 additions and 1 deletions
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17
contrib/win32/win32compat/w32fd.c
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@ -88,6 +88,21 @@ fd_table_initialize()
{
struct w32_io *pio;
HANDLE wh;
char *stdio_mode_env;
int stdio_mode = NONSOCK_SYNC_FD;
stdio_mode_env = getenv("OPENSSH_STDIO_MODE");
if (stdio_mode_env != NULL) {
if (strcmp(stdio_mode_env, "unknown") == 0)
stdio_mode = UNKNOWN_FD;
else if (strcmp(stdio_mode_env, "sock") == 0)
stdio_mode = SOCK_FD;
else if (strcmp(stdio_mode_env, "nonsock") == 0)
stdio_mode = NONSOCK_FD;
else if (strcmp(stdio_mode_env, "nonsock_sync") == 0)
stdio_mode = NONSOCK_SYNC_FD;
}
/* table entries representing std in, out and error*/
DWORD wh_index[] = { STD_INPUT_HANDLE , STD_OUTPUT_HANDLE , STD_ERROR_HANDLE };
int fd_num = 0;
@ -104,7 +119,7 @@ fd_table_initialize()
return -1;
}
memset(pio, 0, sizeof(struct w32_io));
pio->type = NONSOCK_SYNC_FD;
pio->type = stdio_mode;
pio->handle = wh;
fd_table_set(pio, fd_num);
}