net: prevent setting ttl=0 via IP_TTL

A regression is introduced by the following commit:

commit 4d52cfbef6266092d535237ba5a4b981458ab171
Author: Eric Dumazet <[e-mail]>
Date: Tue Jun 2 00:42:16 2009 -0700

net: ipv4/ip_sockglue.c cleanups

Pure cleanups

but it is not a pure cleanup...

- if (val != -1 && (val < 1 || val>255))
+ if (val != -1 && (val < 0 || val > 255))

Since there is no reason provided to allow ttl=0, change it back.

Reported-by: nitin padalia <[e-mail]>
Cc: nitin padalia <[e-mail]>
Cc: Eric Dumazet <[e-mail]>
Cc: David S. Miller <[e-mail]>
Signed-off-by: Cong Wang <[e-mail]>
Acked-by: Eric Dumazet <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/ipv4/ip_sockglue.c

···
 	case IP_TTL:
 		if (optlen < 1)
 			goto e_inval;
-		if (val != -1 && (val < 0 || val > 255))
+		if (val != -1 && (val < 1 || val > 255))
 			goto e_inval;
 		inet->uc_ttl = val;
 		break;