[PATCH] iproute: Properly handle protocol level diag module absence

[Pavel Emelyanov <xemul@parallels.com>]

When *_diag module is missing in the kernel, the ss tool should go
ad read legacry /proc/* files.

This is the case when all *_diag stuff is missing, but in case the
inet_diag.ko is loaded, but (tcp|udp)_diag.ko is not, the ss tool
doesn't notice this and produces empty output. The reason for that
is -- error from the inet_diag module (which means, that e.g. the
udp_diag is missing) is reported in the NLMSG_DONE message body.

That said, we need to check the NLMSG_DONE's message return code
and act respectively.

Reported-by: François-Xavier Le Bail <fx.lebail@yahoo.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

---

diff --git a/misc/ss.c b/misc/ss.c
index 37dcc11..9c7d937 100644
--- a/misc/ss.c
+++ b/misc/ss.c
@@ -1746,8 +1746,15 @@ again:
 			    h->nlmsg_seq != 123456)
 				goto skip_it;
 
-			if (h->nlmsg_type == NLMSG_DONE)
+			if (h->nlmsg_type == NLMSG_DONE) {
+				int *len = (int *)NLMSG_DATA(h);
+				if (*len < 0) {
+					close(fd);
+					return -1;
+				}
+
 				goto done;
+			}
 
 			if (h->nlmsg_type == NLMSG_ERROR) {
 				struct nlmsgerr *err = (struct nlmsgerr*)NLMSG_DATA(h);