From 0dcfa1b0211fa50201d51d0f52869a8e2d93ba76 Mon Sep 17 00:00:00 2001
From: Phil Sutter <psutter@redhat.com>
Date: Mon, 7 Dec 2020 18:29:15 +0100
Subject: [PATCH] json: Fix seqnum_to_json() functionality

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1900565
Upstream Status: nftables commit 299ec575faa6b

commit 299ec575faa6b070940b483dc517ecd883b9f1a4
Author: Phil Sutter <phil@nwl.cc>
Date:   Wed Dec 2 23:07:11 2020 +0100

    json: Fix seqnum_to_json() functionality

    Introduction of json_cmd_assoc_hash missed that by the time the hash
    table insert happens, the struct cmd object's 'seqnum' field which is
    used as key is not initialized yet. This doesn't happen until
    nft_netlink() prepares the batch object which records the lowest seqnum.
    Therefore push all json_cmd_assoc objects into a temporary list until
    the first lookup happens. At this time, all referenced cmd objects have
    their seqnum set and the list entries can be moved into the hash table
    for fast lookups.

    To expose such problems in the future, make json_events_cb() emit an
    error message if the passed message has a handle but no assoc entry is
    found for its seqnum.

    Fixes: 389a0e1edc89a ("json: echo: Speedup seqnum_to_json()")
    Cc: Derek Dai <daiderek@gmail.com>
    Signed-off-by: Phil Sutter <phil@nwl.cc>
---
 src/parser_json.c | 27 +++++++++++++++++++++++----
 1 file changed, 23 insertions(+), 4 deletions(-)

diff --git a/src/parser_json.c b/src/parser_json.c
index 107dc38..785f0e7 100644
--- a/src/parser_json.c
+++ b/src/parser_json.c
@@ -3646,6 +3646,7 @@ static int json_verify_metainfo(struct json_ctx *ctx, json_t *root)
 }
 
 struct json_cmd_assoc {
+	struct json_cmd_assoc *next;
 	struct hlist_node hnode;
 	const struct cmd *cmd;
 	json_t *json;
@@ -3653,6 +3654,7 @@ struct json_cmd_assoc {
 
 #define CMD_ASSOC_HSIZE		512
 static struct hlist_head json_cmd_assoc_hash[CMD_ASSOC_HSIZE];
+static struct json_cmd_assoc *json_cmd_assoc_list;
 
 static void json_cmd_assoc_free(void)
 {
@@ -3660,6 +3662,12 @@ static void json_cmd_assoc_free(void)
 	struct hlist_node *pos, *n;
 	int i;
 
+	while (json_cmd_assoc_list) {
+		cur = json_cmd_assoc_list->next;
+		free(json_cmd_assoc_list);
+		json_cmd_assoc_list = cur;
+	}
+
 	for (i = 0; i < CMD_ASSOC_HSIZE; i++) {
 		hlist_for_each_entry_safe(cur, pos, n,
 					  &json_cmd_assoc_hash[i], hnode)
@@ -3670,21 +3678,29 @@ static void json_cmd_assoc_free(void)
 static void json_cmd_assoc_add(json_t *json, const struct cmd *cmd)
 {
 	struct json_cmd_assoc *new = xzalloc(sizeof *new);
-	int key = cmd->seqnum % CMD_ASSOC_HSIZE;
 
 	new->json	= json;
 	new->cmd	= cmd;
+	new->next	= json_cmd_assoc_list;
 
-	hlist_add_head(&new->hnode, &json_cmd_assoc_hash[key]);
+	json_cmd_assoc_list = new;
 }
 
 static json_t *seqnum_to_json(const uint32_t seqnum)
 {
-	int key = seqnum % CMD_ASSOC_HSIZE;
 	struct json_cmd_assoc *cur;
 	struct hlist_node *n;
+	int key;
 
+	while (json_cmd_assoc_list) {
+		cur = json_cmd_assoc_list;
+		json_cmd_assoc_list = cur->next;
 
+		key = cur->cmd->seqnum % CMD_ASSOC_HSIZE;
+		hlist_add_head(&cur->hnode, &json_cmd_assoc_hash[key]);
+	}
+
+	key = seqnum % CMD_ASSOC_HSIZE;
 	hlist_for_each_entry(cur, n, &json_cmd_assoc_hash[key], hnode) {
 		if (cur->cmd->seqnum == seqnum)
 			return cur->json;
@@ -3865,8 +3881,11 @@ int json_events_cb(const struct nlmsghdr *nlh, struct netlink_mon_handler *monh)
 		return MNL_CB_OK;
 
 	json = seqnum_to_json(nlh->nlmsg_seq);
-	if (!json)
+	if (!json) {
+		json_echo_error(monh, "No JSON command found with seqnum %lu\n",
+				nlh->nlmsg_seq);
 		return MNL_CB_OK;
+	}
 
 	tmp = json_object_get(json, "add");
 	if (!tmp)
-- 
1.8.3.1