Re: [dpdk-dev] [PATCH v1] eal: add strscpy function

["Kuusisaari, Juhamatti (Coriant - FI/Espoo)" <juhamatti.kuusisaari@coriant.com>]

> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Gaetan Rivet
> Sent: Tuesday, September 11, 2018 1:04 PM
> To: dev@dpdk.org
> Cc: Gaetan Rivet <gaetan.rivet@6wind.com>
> Subject: [dpdk-dev] [PATCH v1] eal: add strscpy function
> 
> The strncpy function has long been deemed unsafe for use,
> in favor of strlcpy or snprintf.
> 
> While snprintf is standard and strlcpy is still largely available,
> they both have issues regarding error checking and performance.
> 
> Both will force reading the source buffer past the requested size
> if the input is not a proper c-string, and will return the expected
> number of bytes copied, meaning that error checking needs to verify
> that the number of bytes copied is not superior to the destination
> size.
> 
> This contributes to awkward code flow, unclear error checking and
> potential issues with malformed input.
> 
> The function strscpy has been discussed for some time already and
> has been made available in the linux kernel[1].
> 
> Propose this new function as a safe alternative.
> 
> [1]:
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i
> d=30c44659f4a3e7e1f9f47e895591b4b40bf62671
> 
> Signed-off-by: Gaetan Rivet <gaetan.rivet@6wind.com>
> ---
> 
> I agree with the original email, here is a proposed implementation.
> I have added the function as part of 18.11 API proper, because this API
> is definitely not meant to change.
> 
> This is not meant to be enforced on existing code, or even on new code.
> But I think it is better to have it available.
> 
>  lib/librte_eal/common/eal_common_string_fns.c | 30
> +++++++++++++++++++
>  .../common/include/rte_string_fns.h           | 23 ++++++++++++++
>  lib/librte_eal/rte_eal_version.map            |  7 +++++
>  3 files changed, 60 insertions(+)
> 
> diff --git a/lib/librte_eal/common/eal_common_string_fns.c
> b/lib/librte_eal/common/eal_common_string_fns.c
> index 6ac5f8289..8a34d2422 100644
> --- a/lib/librte_eal/common/eal_common_string_fns.c
> +++ b/lib/librte_eal/common/eal_common_string_fns.c
> @@ -38,3 +38,33 @@ rte_strsplit(char *string, int stringlen,
>  	errno = EINVAL;
>  	return -1;
>  }
> +
> +/* Copy src string into dst.
> + *
> + * Return negative value and NUL-terminate if dst is too short,
> + * Otherwise return number of bytes copied.
> + */
> +ssize_t
> +strscpy(char *dst, const char *src, size_t dsize)
> +{
> +	const char *osrc = src;
> +	size_t nleft = dsize;
> +
> +	/* Copy as many bytes as will fit. */
> +	if (nleft != 0) {
> +		while (--nleft != 0) {
> +			if ((*dst++ = *src++) == '\0')
> +				break;
> +		}
> +	}
> +
> +	/* Not enough room in dst, add NUL and return error. */
> +	if (nleft == 0) {
> +		if (dsize != 0)
> +			*dst = '\0';
> +		return -E2BIG;
> +	}
> +
> +	/* count does not include NUL */
> +	return (src - osrc - 1);
> +}
> diff --git a/lib/librte_eal/common/include/rte_string_fns.h
> b/lib/librte_eal/common/include/rte_string_fns.h
> index 97597a148..46dd919b4 100644
> --- a/lib/librte_eal/common/include/rte_string_fns.h
> +++ b/lib/librte_eal/common/include/rte_string_fns.h
> @@ -76,6 +76,29 @@ rte_strlcpy(char *dst, const char *src, size_t size)
>  #endif /* RTE_USE_LIBBSD */
>  #endif /* BSDAPP */
> 
> +/**
> + * Copy string src to buffer dst of size dsize.
> + * At most dsize-1 chars will be copied.
> + * Always NUL-terminates, unless (dsize == 0).
> + * Returns number of bytes copied (terminating NUL-byte excluded) on
> success.
> + * Negative errno on error.
> + *
> + * @param dst
> + *   The destination string.
> + *
> + * @param src
> + *   The input string to be copied.
> + *
> + * @param dsize
> + *   Length in bytes of the destination buffer.
> + *
> + * @return
> + *   The number of bytes copied on success
> + *   -E2BIG if the destination buffer is too small.
> + */
> +ssize_t
> +strscpy(char *dst, const char *src, size_t dsize);
> +
>  #ifdef __cplusplus
>  }
>  #endif
> diff --git a/lib/librte_eal/rte_eal_version.map
> b/lib/librte_eal/rte_eal_version.map
> index 344a43d32..fc7b50669 100644
> --- a/lib/librte_eal/rte_eal_version.map
> +++ b/lib/librte_eal/rte_eal_version.map
> @@ -262,6 +262,13 @@ DPDK_18.08 {
> 
>  } DPDK_18.05;
> 
> +DPDK_18.11 {
> +	global:
> +
> +	strscpy;
> +
> +} DPDK_18.08;
> +
>  EXPERIMENTAL {
>  	global:

Acked-by: Juhamatti Kuusisaari <juhamatti.kuusisaari@coriant.com>

> --
> 2.18.0