[PATCH] tap: Fix EAGAIN/EWOULDBLOCK check in tap_pasta_input()

[PATCH] tap: Fix EAGAIN/EWOULDBLOCK check in tap_pasta_input()

[Hayato Kiwata]

On Linux, EAGAIN and EWOULDBLOCK have the same value. Commit
d2a1dc744b10 ("tap: Restructure in tap_pasta_input()") added a check for
EWOULDBLOCK on purpose:

> - Check for EWOULDBLOCK as well as EAGAIN for the benefit of any future
>   ports where those might not have the same value

However, the condition uses && instead of ||, so it can never be true on a
platform where EAGAIN and EWOULDBLOCK are different.

Use || instead so that the check works as intended on such platforms.

Fixes: d2a1dc744b10 ("tap: Restructure in tap_pasta_input()")

Signed-off-by: Hayato Kiwata <dev@haytok.jp>
---
 tap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tap.c b/tap.c
index d418961..cf87591 100644
--- a/tap.c
+++ b/tap.c
@@ -1329,7 +1329,7 @@ static void tap_pasta_input(struct ctx *c, const struct timespec *now)
 				continue;
 			}
 
-			if (errno == EAGAIN && errno == EWOULDBLOCK)
+			if (errno == EAGAIN || errno == EWOULDBLOCK)
 				break; /* all done for now */
 
 			die("Error on tap device, exiting");
-- 
2.39.5 (Apple Git-154)

Re: [PATCH] tap: Fix EAGAIN/EWOULDBLOCK check in tap_pasta_input()

[David Gibson]

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On Fri, Jul 17, 2026 at 02:21:21AM +0900, Hayato Kiwata wrote:
> On Linux, EAGAIN and EWOULDBLOCK have the same value. Commit
> d2a1dc744b10 ("tap: Restructure in tap_pasta_input()") added a check for
> EWOULDBLOCK on purpose:
> 
> > - Check for EWOULDBLOCK as well as EAGAIN for the benefit of any future
> >   ports where those might not have the same value
> 
> However, the condition uses && instead of ||, so it can never be true on a
> platform where EAGAIN and EWOULDBLOCK are different.
> 
> Use || instead so that the check works as intended on such platforms.
> 
> Fixes: d2a1dc744b10 ("tap: Restructure in tap_pasta_input()")
> 
> Signed-off-by: Hayato Kiwata <dev@haytok.jp>

Oops, mea culpa.

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

> ---
>  tap.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tap.c b/tap.c
> index d418961..cf87591 100644
> --- a/tap.c
> +++ b/tap.c
> @@ -1329,7 +1329,7 @@ static void tap_pasta_input(struct ctx *c, const struct timespec *now)
>  				continue;
>  			}
>  
> -			if (errno == EAGAIN && errno == EWOULDBLOCK)
> +			if (errno == EAGAIN || errno == EWOULDBLOCK)
>  				break; /* all done for now */
>  
>  			die("Error on tap device, exiting");
> -- 
> 2.39.5 (Apple Git-154)
> 

-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson

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