iptables/0028-xtables-monitor-fix-rule-printing.patch

From 524f17b1027cb3b6bd5484c644d4dc226d137d91 Mon Sep 17 00:00:00 2001
From: Florian Westphal <fw@strlen.de>
Date: Sat, 12 Dec 2020 16:15:32 +0100
Subject: [PATCH] xtables-monitor: fix rule printing

trace_print_rule does a rule dump.  This prints unrelated rules
in the same chain.  Instead the function should only request the
specific handle.

Furthermore, flush output buffer afterwards so this plays nice when
output isn't a terminal.

Signed-off-by: Florian Westphal <fw@strlen.de>
(cherry picked from commit 07af4da52ab3002c9cb510863b4eb7aaca4fb43b)
---
 iptables/xtables-monitor.c | 32 +++++++++++++++-----------------
 1 file changed, 15 insertions(+), 17 deletions(-)

diff --git a/iptables/xtables-monitor.c b/iptables/xtables-monitor.c
index 4008cc00d4694..364e600e1b38a 100644
--- a/iptables/xtables-monitor.c
+++ b/iptables/xtables-monitor.c
@@ -227,12 +227,12 @@ static void trace_print_rule(const struct nftnl_trace *nlt, struct cb_arg *args)
 		exit(EXIT_FAILURE);
 	}
 
-	nlh = nftnl_chain_nlmsg_build_hdr(buf, NFT_MSG_GETRULE, family, NLM_F_DUMP, 0);
+	nlh = nftnl_chain_nlmsg_build_hdr(buf, NFT_MSG_GETRULE, family, 0, 0);
 
         nftnl_rule_set_u32(r, NFTNL_RULE_FAMILY, family);
 	nftnl_rule_set_str(r, NFTNL_RULE_CHAIN, chain);
 	nftnl_rule_set_str(r, NFTNL_RULE_TABLE, table);
-	nftnl_rule_set_u64(r, NFTNL_RULE_POSITION, handle);
+	nftnl_rule_set_u64(r, NFTNL_RULE_HANDLE, handle);
 	nftnl_rule_nlmsg_build_payload(nlh, r);
 	nftnl_rule_free(r);
 
@@ -248,24 +248,21 @@ static void trace_print_rule(const struct nftnl_trace *nlt, struct cb_arg *args)
 	}
 
 	portid = mnl_socket_get_portid(nl);
-        if (mnl_socket_sendto(nl, nlh, nlh->nlmsg_len) < 0) {
-                perror("mnl_socket_send");
-                exit(EXIT_FAILURE);
-        }
+	if (mnl_socket_sendto(nl, nlh, nlh->nlmsg_len) < 0) {
+		perror("mnl_socket_send");
+		exit(EXIT_FAILURE);
+	}
 
 	ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
-        while (ret > 0) {
+	if (ret > 0) {
 		args->is_event = false;
-                ret = mnl_cb_run(buf, ret, 0, portid, rule_cb, args);
-                if (ret <= 0)
-                        break;
-                ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
-        }
-        if (ret == -1) {
-                perror("error");
-                exit(EXIT_FAILURE);
-        }
-        mnl_socket_close(nl);
+		ret = mnl_cb_run(buf, ret, 0, portid, rule_cb, args);
+	}
+	if (ret == -1) {
+		perror("error");
+		exit(EXIT_FAILURE);
+	}
+	mnl_socket_close(nl);
 }
 
 static void trace_print_packet(const struct nftnl_trace *nlt, struct cb_arg *args)
@@ -531,6 +528,7 @@ static int trace_cb(const struct nlmsghdr *nlh, struct cb_arg *arg)
 err_free:
 	nftnl_trace_free(nlt);
 err:
+	fflush(stdout);
 	return MNL_CB_OK;
 }
 
-- 
2.40.0