nexthop: Simplify nexthop bucket dump

Before commit f10d3d9d ("nexthop: Make nexthop bucket dump more
efficient"), rtm_dump_nexthop_bucket_nh() returned a non-zero return
code for each resilient nexthop group whose buckets it dumped,
regardless if it encountered an error or not.

This meant that the sentinel ('dd->ctx->nh.idx') used by the function
that walked the different nexthops could not be used as a sentinel for
the bucket dump, as otherwise buckets from the same group would be
dumped over and over again.

This was dealt with by adding another sentinel ('dd->ctx->done_nh_idx')
that was incremented by rtm_dump_nexthop_bucket_nh() after successfully
dumping all the buckets from a given group.

After the previously mentioned commit this sentinel is no longer
necessary since the function no longer returns a non-zero return code
when successfully dumping all the buckets from a given group.

Remove this sentinel and simplify the code.
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://lore.kernel.org/r/20230813164856.2379822-2-idosch@nvidia.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/ipv4/nexthop.c

@@ -3337,7 +3337,6 @@ static int nh_valid_dump_bucket_req(const struct nlmsghdr *nlh,
 struct rtm_dump_res_bucket_ctx {
 	struct rtm_dump_nh_ctx nh;
 	u16 bucket_index;
-	u32 done_nh_idx; /* 1 + the index of the last fully processed NH. */
 };
 
 static struct rtm_dump_res_bucket_ctx *
@@ -3366,9 +3365,6 @@ static int rtm_dump_nexthop_bucket_nh(struct sk_buff *skb,
 	u16 bucket_index;
 	int err;
 
-	if (dd->ctx->nh.idx < dd->ctx->done_nh_idx)
-		return 0;
-
 	nhg = rtnl_dereference(nh->nh_grp);
 	res_table = rtnl_dereference(nhg->res_table);
 	for (bucket_index = dd->ctx->bucket_index;
@@ -3395,7 +3391,6 @@ static int rtm_dump_nexthop_bucket_nh(struct sk_buff *skb,
 			return err;
 	}
 
-	dd->ctx->done_nh_idx = dd->ctx->nh.idx + 1;
 	dd->ctx->bucket_index = 0;
 
 	return 0;