[PATCH v2 13/23] nscd: Introduce __nscd_read_from_socket client function

[Carlos O'Donell]

On 3/20/26 4:42 PM, Florian Weimer wrote:

LGTM.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

> ---
>   nscd/nscd-client.h | 20 ++++++++++++++++-
>   nscd/nscd_helper.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++
>   2 files changed, 72 insertions(+), 1 deletion(-)
> 
> diff --git a/nscd/nscd-client.h b/nscd/nscd-client.h
> index c507933acb..10284e8ef2 100644
> --- a/nscd/nscd-client.h
> +++ b/nscd/nscd-client.h
> @@ -366,11 +366,29 @@ struct mapped_database
>     __libc_rwlock_define (, lock);
>   };
>   
> -/* Open socket connection to nscd server.  */
> +/* Open socket connection to nscd server, send the request, and read
> +   the start of the response (update to RESPONSELEN bytes).  If the
> +   procided response buffer is exceeded, the socket is left open, so
> +   that more data can be read.  */
>   extern int __nscd_open_socket (const char *key, size_t keylen,
>   			       request_type type, void *response,
>   			       size_t responselen) attribute_hidden;
>   
> +/* Open a socket to nscd, send the request, and read the full
> +   response.  *RESPONSE is grown as necessary.
> +
> +   A non-negative return value indicates the number of response bytes
> +   stored at RESPONSE->data.  The response includes only the struct
> +   *_response_header and the data that follows it, not struct
> +   datahead.
> +
> +   On error, return a negative errno code.  */
> +struct scratch_buffer;
> +ssize_t __nscd_read_from_socket (const char *key, size_t keylen,
> +				 request_type type,
> +				 struct scratch_buffer *response)
> +  attribute_hidden;
> +
>   /* Acquire reference to the mapping for DB (see <nscd-dbtype.h>).  On
>      success, return a pointer to the mapping descriptor, and lock the
>      mapping.
> diff --git a/nscd/nscd_helper.c b/nscd/nscd_helper.c
> index 9bd0e7818e..ed2d8d09da 100644
> --- a/nscd/nscd_helper.c
> +++ b/nscd/nscd_helper.c
> @@ -37,6 +37,7 @@
>   #include <kernel-features.h>
>   #include <nss.h>
>   #include <struct___timespec64.h>
> +#include <scratch_buffer.h>
>   
>   #include "nscd-client.h"
>   #include "nscd-dbtype.h"
> @@ -612,3 +613,55 @@ __nscd_open_socket (const char *key, size_t keylen, request_type type,
>   
>     return -1;
>   }
> +
> +ssize_t
> +__nscd_read_from_socket (const char *key, size_t keylen, request_type type,
> +			 struct scratch_buffer *response)
> +{
> +  if (keylen > MAXKEYLEN)
> +    return -ENAMETOOLONG;
> +
> +  int sock = open_socket (type, key, keylen);

OK. Pass type, key and keylen to open_socket helper (used by __nscd_get_mapping,
and __nscd_open_socket).

> +  if (sock < 0)
> +    return sock;
> +
> +  /* The nscd stream protocol does not size information in a way that
> +     is independent of request type.  However, there is only one
> +     request per connection, so the code below simply reads all data
> +     that is available before end of stream.  */
> +
> +  ssize_t ret = 0;		/* Number of bytes read, or -1 on error.  */
> +  while (true)
> +    {
> +      /* Wait for data.  Give up on timeout.  */
> +      if (wait_on_socket (sock, 5 * 1000) == 0)
> +	break;
> +      size_t remaining = response->length - ret;
> +      ssize_t nbytes = TEMP_FAILURE_RETRY (__read (sock, response->data + ret,
> +						   remaining));
> +      if (nbytes < 0)
> +	{
> +	  ret = -errno;
> +	  break;
> +	}
> +      if (nbytes == 0)
> +	/* The end of the stream marks the end of packet.  We cannot
> +	   tell if the data was truncated because nscd went away
> +	   unexpectedly.  This will be recognized by the caller during
> +	   packet parsing.  */
> +	break;
> +
> +      /* Try reading more data in the next iteration after growing the
> +	 buffer.  */
> +      ret += nbytes;
> +      if (ret == response->length && !scratch_buffer_grow_preserve (response))
> +	{
> +	  ret = -ENOMEM;
> +	  break;
> +	}
> +    }
> +
> +  __close_nocancel_nostatus (sock);
> +
> +  return ret;
> +}


-- 
Cheers,
Carlos.