dhcpcd-discuss

Hi Peter

On 19/05/2014 19:04, Peter Mattern wrote:
> Hello.
>
> I'm just trying to debug the message
>           dhcpcd[<PID>]: dhcp6_start: <interface>: Protocol not 
> available
> that appears if a Cubietruck running Arch Linux tries to connect to an
> IPv6-enabled router, right after receiving Router Advertisements.
>
> Obviously the problem behind the message must be related to DHCPv6.
> But neither dhcpcd nor the upstream router are at fault imo as the
> message can't be seen if other devices running Arch Linux i686 or
> x86-64 connect to the same router. Moreover, it makes no difference
> whether the connection is established via WLAN or Ethernet. I also
> tried to find differences in the packages installed and Kernel config
> files used in the different flavours of Arch Linux but without
> success.
>
> So I would like to ask whether You could give me a hint at the exact
> meaning of the said message.

After looking at this report, I checked the code and made the following 
change:
http://roy.marples.name/projects/dhcpcd/info/ea6ed21cdb

Sockets would be opened with PF_*, not AF_*.
Now, on supported OS's, AF_INET6 will always be equal to PF_INET6 so 
this shouldn't make any difference but it's the more correct thing to 
do.

Anyway, one of the below calls would be failing:

	ctx->dhcp_fd = socket(PF_INET6,
	    SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK,
	    IPPROTO_UDP);
	if (setsockopt(ctx->dhcp_fd, SOL_SOCKET, SO_REUSEADDR,
	    &n, sizeof(n)) == -1)
		goto errexit;

	if (setsockopt(ctx->dhcp_fd, SOL_SOCKET, SO_BROADCAST,
	    &n, sizeof(n)) == -1)
		goto errexit;

#ifdef SO_REUSEPORT
	if (setsockopt(ctx->dhcp_fd, SOL_SOCKET, SO_REUSEPORT,
	    &n, sizeof(n)) == -1)
		goto errexit;
#endif

The chances are it is the first one.
You can do test this by adding debug lines such as `printf("0\n");` to 
the code and watching what gets printed before the error.
I've attached a patch to the latest head to demonstrate this.
Let me know if I can help more.

Roy

Index: dhcp6.c
==================================================================
--- dhcp6.c
+++ dhcp6.c
@@ -2494,10 +2494,11 @@
 	sa.sin6_port = htons(DHCP6_CLIENT_PORT);
 #ifdef BSD
 	sa.sin6_len = sizeof(sa);
 #endif
 
+	printf("d6_open 0\n");
 	ctx = dctx->ipv6;
 #ifdef SOCK_CLOEXEC
 	ctx->dhcp_fd = socket(PF_INET6,
 	    SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK,
 	    IPPROTO_UDP);
@@ -2520,30 +2521,35 @@
 		ctx->dhcp_fd = -1;
 	        return -1;
 	}
 #endif
 
+	printf("d6_open 1\n");
 	n = 1;
 	if (setsockopt(ctx->dhcp_fd, SOL_SOCKET, SO_REUSEADDR,
 	    &n, sizeof(n)) == -1)
 		goto errexit;
 
+	printf("d6_open 2\n");
 	n = 1;
 	if (setsockopt(ctx->dhcp_fd, SOL_SOCKET, SO_BROADCAST,
 	    &n, sizeof(n)) == -1)
 		goto errexit;
 
+	printf("d6_open 3\n");
 #ifdef SO_REUSEPORT
 	n = 1;
 	if (setsockopt(ctx->dhcp_fd, SOL_SOCKET, SO_REUSEPORT,
 	    &n, sizeof(n)) == -1)
 		goto errexit;
 #endif
 
+	printf("d6_open 5\n");
 	if (bind(ctx->dhcp_fd, (struct sockaddr *)&sa, sizeof(sa)) == -1)
 		goto errexit;
 
+	printf("d6_open 6\n");
 	n = 1;
 	if (setsockopt(ctx->dhcp_fd, IPPROTO_IPV6, IPV6_RECVPKTINFO,
 	    &n, sizeof(n)) == -1)
 		goto errexit;