netdev - [PATCH] iptables: flush stdout after every verbose log.

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Message-Id: <20200421081542.108296-1-zenczykowski@gmail.com>
Date:   Tue, 21 Apr 2020 01:15:42 -0700
From:   Maciej Żenczykowski <zenczykowski@...il.com>
To:     Maciej Żenczykowski <maze@...gle.com>,
        Pablo Neira Ayuso <pablo@...filter.org>,
        Florian Westphal <fw@...len.de>
Cc:     Linux Network Development Mailing List <netdev@...r.kernel.org>,
        Netfilter Development Mailing List 
        <netfilter-devel@...r.kernel.org>
Subject: [PATCH] iptables: flush stdout after every verbose log.

From: Maciej Żenczykowski <maze@...gle.com>

Ensures that each logged line is flushed to stdout after it's
written, and not held in any buffer.

Places to modify found via:
  git grep -C5 'fputs[(]buffer, stdout[)];'

On Android iptables-restore -v is run as netd daemon's child process
and fed actions via pipe.  '#PING' is used to verify the child
is still responsive, and thus needs to be unbuffered.

Luckily if you're running iptables-restore in verbose mode you
probably either don't care about performance or - like Android
- actually need this.

Test: builds, required on Android for ip6?tables-restore netd
  subprocess health monitoring.
Signed-off-by: Maciej Żenczykowski <maze@...gle.com>
---
 iptables/iptables-restore.c | 4 +++-
 iptables/xtables-restore.c  | 4 +++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/iptables/iptables-restore.c b/iptables/iptables-restore.c
index b0a51d49..fea04842 100644
--- a/iptables/iptables-restore.c
+++ b/iptables/iptables-restore.c
@@ -178,8 +178,10 @@ ip46tables_restore_main(const struct iptables_restore_cb *cb,
 		if (buffer[0] == '\n')
 			continue;
 		else if (buffer[0] == '#') {
-			if (verbose)
+			if (verbose) {
 				fputs(buffer, stdout);
+				fflush(stdout);
+			}
 			continue;
 		} else if ((strcmp(buffer, "COMMIT\n") == 0) && (in_table)) {
 			if (!testing) {
diff --git a/iptables/xtables-restore.c b/iptables/xtables-restore.c
index c472ac9b..8c25e5b2 100644
--- a/iptables/xtables-restore.c
+++ b/iptables/xtables-restore.c
@@ -85,8 +85,10 @@ static void xtables_restore_parse_line(struct nft_handle *h,
 	if (buffer[0] == '\n')
 		return;
 	else if (buffer[0] == '#') {
-		if (verbose)
+		if (verbose) {
 			fputs(buffer, stdout);
+			fflush(stdout);
+		}
 		return;
 	} else if (state->in_table &&
 		   (strncmp(buffer, "COMMIT", 6) == 0) &&
-- 
2.26.1.301.g55bc3eb7cb9-goog