Merge branch 'nexthop-nexthop-dump-fixes'

Ido Schimmel says:

====================
nexthop: Nexthop dump fixes

Patches #1 and #3 fix two problems related to nexthops and nexthop
buckets dump, respectively. Patch #2 is a preparation for the third
patch.

The pattern described in these patches of splitting the NLMSG_DONE to a
separate response is prevalent in other rtnetlink dump callbacks. I
don't know if it's because I'm missing something or if this was done
intentionally to ensure the message is delivered to user space. After
commit 0642840 ("af_netlink: ensure that NLMSG_DONE never fails in
dumps") this is no longer necessary and I can improve these dump
callbacks assuming this analysis is correct.

No regressions in existing tests:

 # ./fib_nexthops.sh
 [...]
 Tests passed: 230
 Tests failed:   0
====================

Link: https://lore.kernel.org/r/20230808075233.3337922-1-idosch@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/ipv4/nexthop.c

@@ -3221,13 +3221,9 @@ static int rtm_dump_nexthop(struct sk_buff *skb, struct netlink_callback *cb)
 				     &rtm_dump_nexthop_cb, &filter);
 	if (err < 0) {
 		if (likely(skb->len))
-			goto out;
-		goto out_err;
+			err = skb->len;
 	}
 
-out:
-	err = skb->len;
-out_err:
 	cb->seq = net->nexthop.seq;
 	nl_dump_check_consistent(cb, nlmsg_hdr(skb));
 	return err;
@@ -3367,25 +3363,19 @@ static int rtm_dump_nexthop_bucket_nh(struct sk_buff *skb,
 		    dd->filter.res_bucket_nh_id != nhge->nh->id)
 			continue;
 
+		dd->ctx->bucket_index = bucket_index;
 		err = nh_fill_res_bucket(skb, nh, bucket, bucket_index,
 					 RTM_NEWNEXTHOPBUCKET, portid,
 					 cb->nlh->nlmsg_seq, NLM_F_MULTI,
 					 cb->extack);
-		if (err < 0) {
-			if (likely(skb->len))
-				goto out;
-			goto out_err;
-		}
+		if (err)
+			return err;
 	}
 
 	dd->ctx->done_nh_idx = dd->ctx->nh.idx + 1;
-	bucket_index = 0;
+	dd->ctx->bucket_index = 0;
 
-out:
-	err = skb->len;
-out_err:
-	dd->ctx->bucket_index = bucket_index;
-	return err;
+	return 0;
 }
 
 static int rtm_dump_nexthop_bucket_cb(struct sk_buff *skb,
@@ -3434,13 +3424,9 @@ static int rtm_dump_nexthop_bucket(struct sk_buff *skb,
 
 	if (err < 0) {
 		if (likely(skb->len))
-			goto out;
-		goto out_err;
+			err = skb->len;
 	}
 
-out:
-	err = skb->len;
-out_err:
 	cb->seq = net->nexthop.seq;
 	nl_dump_check_consistent(cb, nlmsg_hdr(skb));
 	return err;

tools/testing/selftests/net/fib_nexthops.sh

@@ -1981,6 +1981,11 @@ basic()
 
 	run_cmd "$IP link set dev lo up"
 
+	# Dump should not loop endlessly when maximum nexthop ID is configured.
+	run_cmd "$IP nexthop add id $((2**32-1)) blackhole"
+	run_cmd "timeout 5 $IP nexthop"
+	log_test $? 0 "Maximum nexthop ID dump"
+
 	#
 	# groups
 	#
@@ -2201,6 +2206,11 @@ basic_res()
 	run_cmd "$IP nexthop bucket list fdb"
 	log_test $? 255 "Dump all nexthop buckets with invalid 'fdb' keyword"
 
+	# Dump should not loop endlessly when maximum nexthop ID is configured.
+	run_cmd "$IP nexthop add id $((2**32-1)) group 1/2 type resilient buckets 4"
+	run_cmd "timeout 5 $IP nexthop bucket"
+	log_test $? 0 "Maximum nexthop ID dump"
+
 	#
 	# resilient nexthop buckets get requests
 	#