netdev - Re: [PATCH iproute2 v2] libgenl: make genl_add_mcast

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Date:   Sun, 16 May 2021 20:38:12 -0600
From:   David Ahern <dsahern@...il.com>
To:     Florian Westphal <fw@...len.de>, netdev@...r.kernel.org
Subject: Re: [PATCH iproute2 v2] libgenl: make genl_add_mcast_grp set errno on
 error

On 5/10/21 6:06 AM, Florian Westphal wrote:
> diff --git a/lib/libgenl.c b/lib/libgenl.c
> index 4c51d47af46b..8b22c06e7941 100644
> --- a/lib/libgenl.c
> +++ b/lib/libgenl.c
> @@ -84,6 +84,7 @@ static int genl_parse_grps(struct rtattr *attr, const char *name, unsigned int *
>  		}
>  	}
>  
> +	errno = ENOENT;
>  	return -1;
>  }
>  
> @@ -108,17 +109,22 @@ int genl_add_mcast_grp(struct rtnl_handle *grth, __u16 fnum, const char *group)
>  	ghdr = NLMSG_DATA(answer);
>  	len = answer->nlmsg_len;
>  
> -	if (answer->nlmsg_type != GENL_ID_CTRL)
> +	if (answer->nlmsg_type != GENL_ID_CTRL) {
> +		errno = EINVAL;
>  		goto err_free;
> +	}
>  
>  	len -= NLMSG_LENGTH(GENL_HDRLEN);
> -	if (len < 0)
> +	if (len < 0) {
> +		errno = EINVAL;
>  		goto err_free;
> +	}
>  
>  	attrs = (struct rtattr *) ((char *) ghdr + GENL_HDRLEN);
>  	parse_rtattr(tb, CTRL_ATTR_MAX, attrs, len);
>  
>  	if (tb[CTRL_ATTR_MCAST_GROUPS] == NULL) {
> +		errno = ENOENT;
>  		fprintf(stderr, "Missing mcast groups TLV\n");
>  		goto err_free;
>  	}
> 

I get compile errors on Ubuntu 20.04:


lib
    CC       libgenl.o
libgenl.c: In function ‘genl_parse_grps’:
libgenl.c:87:2: error: ‘errno’ undeclared (first use in this function)
   87 |  errno = ENOENT;
      |  ^~~~~
libgenl.c:12:1: note: ‘errno’ is defined in header ‘<errno.h>’; did you
forget to ‘#include <errno.h>’?
   11 | #include "libgenl.h"
  +++ |+#include <errno.h>
   12 |
libgenl.c:87:2: note: each undeclared identifier is reported only once
for each function it appears in
   87 |  errno = ENOENT;
      |  ^~~~~
libgenl.c:87:10: error: ‘ENOENT’ undeclared (first use in this function)
   87 |  errno = ENOENT;
      |          ^~~~~~
libgenl.c: In function ‘genl_add_mcast_grp’:
libgenl.c:113:3: error: ‘errno’ undeclared (first use in this function)
  113 |   errno = EINVAL;
      |   ^~~~~
libgenl.c:113:3: note: ‘errno’ is defined in header ‘<errno.h>’; did you
forget to ‘#include <errno.h>’?
libgenl.c:113:11: error: ‘EINVAL’ undeclared (first use in this function)
  113 |   errno = EINVAL;
      |           ^~~~~~
libgenl.c:127:11: error: ‘ENOENT’ undeclared (first use in this function)
  127 |   errno = ENOENT;