[PATCH] alfred: add more verbose error message

[PATCH] alfred: add more verbose error message

[noahbpeterson1997]

There is an issue with some Linux distributions (Raspian) where network interfaces are up and
active, but do not have the correct link-local address. This condition is now checked and
output to stderr to better help users troubleshoot this issue.

Signed-off-by: Noah Peterson noahbpeterson1997@gmail.com
---
netsock.c | 18 +++++++++++++++++-
1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/netsock.c b/netsock.c
index feed21d..04f95c7 100644
--- a/netsock.c
+++ b/netsock.c
@@ -322,7 +322,23 @@ static int netsock_open(struct globals *globals, struct interface *interface)
        enable_raw_bind_capability(0);
 
        if (bind(sock, (struct sockaddr *)&sin6, sizeof(sin6)) < 0) {
-               perror("can't bind");
+               if (errno == EADDRNOTAVAIL)
+                       fprintf(stderr, "can't bind to interface %s; "
+                               "expected ipv6 address not found: "
+                               "%02x%02x::%02x%02x:%02x%02x:%02x%02x:%02x%02x\n",
+                               interface->interface,
+                               (int)interface->address.ipv6.s6_addr[0],
+                               (int)interface->address.ipv6.s6_addr[1],
+                               (int)interface->address.ipv6.s6_addr[8],
+                               (int)interface->address.ipv6.s6_addr[9],
+                               (int)interface->address.ipv6.s6_addr[10],
+                               (int)interface->address.ipv6.s6_addr[11],
+                               (int)interface->address.ipv6.s6_addr[12],
+                               (int)interface->address.ipv6.s6_addr[13],
+                               (int)interface->address.ipv6.s6_addr[14],
+                               (int)interface->address.ipv6.s6_addr[15]);
+               else
+                       perror("can't bind");
                goto err;
        }

Re: [PATCH] alfred: add more verbose error message

[Sven Eckelmann]

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On Sunday, 8 September 2024 22:46:05 CEST noahbpeterson1997@gmail.com wrote:
> diff --git a/netsock.c b/netsock.c
> index feed21d..04f95c7 100644
> --- a/netsock.c
> +++ b/netsock.c
> @@ -322,7 +322,23 @@ static int netsock_open(struct globals *globals, struct interface *interface)
>         enable_raw_bind_capability(0);
>  
>         if (bind(sock, (struct sockaddr *)&sin6, sizeof(sin6)) < 0) {
> -               perror("can't bind");
> +               if (errno == EADDRNOTAVAIL)
> +                       fprintf(stderr, "can't bind to interface %s; "
> +                               "expected ipv6 address not found: "
> +                               "%02x%02x::%02x%02x:%02x%02x:%02x%02x:%02x%02x\n",
> +                               interface->interface,
> +                               (int)interface->address.ipv6.s6_addr[0],
> +                               (int)interface->address.ipv6.s6_addr[1],
> +                               (int)interface->address.ipv6.s6_addr[8],
> +                               (int)interface->address.ipv6.s6_addr[9],
> +                               (int)interface->address.ipv6.s6_addr[10],
> +                               (int)interface->address.ipv6.s6_addr[11],
> +                               (int)interface->address.ipv6.s6_addr[12],
> +                               (int)interface->address.ipv6.s6_addr[13],
> +                               (int)interface->address.ipv6.s6_addr[14],
> +                               (int)interface->address.ipv6.s6_addr[15]);
> +               else
> +                       perror("can't bind");
>                 goto err;
>         }

Ehrm, no - this is not a valid way to print IPv6 addresses and it makes to 
many assumptions about the IPv6 address - which will then lead to more 
problems in the future. For creating the ip address string:

    		char ipstr_buf[INET6_ADDRSTRLEN];
    		const char *ipstr;
    		....
    		ipstr = inet_ntop(AF_INET6, &interface->address.ipv6.s6_addr,
    				  ipstr_buf, INET6_ADDRSTRLEN);


Kind regards,
	Sven

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