[PATCH] Temporary patch for arpd

[Pascal <pascal@pascalhp.net>]

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Hello. I found wonderful bug in arpd daemon of iproute2 package.
Somehow arpd is absolute unworkable if run program with -f flag. On my
amd64 server i got "Segmentation fault" regardless -f mac-list.txt file
content.
The source of misc/arpd.c is not hard and i found that cause of
this bug is commit dd50247dba85255538d659551305b4bb75bcae62. I'm not
c++ developer, but i suppose segfault occured because argument of
dbase->put() has non-initialized dbdat.data argument.
Also arpd.c has strange condition "if (do_load || do_list)" that not
allows to run program with -f argument.
I did pull out the hexstring_a2n function from utils.c of previous commit
aeb199d5ce86c6c72decaac333cad5a7d7b38b3a and used it to populate
dbdat.data value after which program works fine.
I hurriedly make the patch that makes program alive. Please inspect
this problem, fix this bug and test program with -f key.
PS: sorry for my english =)

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From 433147a7303c418845bdb5668910caababf79453 Mon Sep 17 00:00:00 2001
From: Pascal <pascal@pascalhp.net>
Date: Wed, 12 Oct 2016 03:13:53 +0800
Subject: [PATCH] Temporary patch for arpd

---
 misc/arpd.c | 44 ++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 42 insertions(+), 2 deletions(-)

diff --git a/misc/arpd.c b/misc/arpd.c
index bfab445..567df5b 100644
--- a/misc/arpd.c
+++ b/misc/arpd.c
@@ -584,6 +584,43 @@ static void send_stats(void)
 	do_stats = 0;
 }
 
+__u8* hexstring_a2n_old(const char *str, __u8 *buf, int blen)
+{
+	int cnt = 0;
+
+	for (;;) {
+		unsigned acc;
+		char ch;
+
+		acc = 0;
+
+		while ((ch = *str) != ':' && ch != 0) {
+			if (ch >= '0' && ch <= '9')
+				ch -= '0';
+			else if (ch >= 'a' && ch <= 'f')
+				ch -= 'a'-10;
+			else if (ch >= 'A' && ch <= 'F')
+				ch -= 'A'-10;
+			else
+				return NULL;
+			acc = (acc<<4) + ch;
+			str++;
+		}
+
+		if (acc > 255)
+			return NULL;
+		if (cnt < blen) {
+			buf[cnt] = acc;
+			cnt++;
+		}
+		if (ch == 0)
+			break;
+		++str;
+	}
+	if (cnt < blen)
+		memset(buf+cnt, 0, blen-cnt);
+	return buf;
+}
 
 int main(int argc, char **argv)
 {
@@ -715,8 +752,11 @@ int main(int argc, char **argv)
 				goto do_abort;
 			}
 
-			if (ll_addr_a2n((char *) b1, 6, macbuf) != 6)
+			dbdat.data = hexstring_a2n_old(macbuf, b1, 6);
+			if (dbdat.data == NULL) {
+				fprintf(stderr, "Invalid MAC address: \"%s\"\n", macbuf);
 				goto do_abort;
+			}
 			dbdat.size = 6;
 
 			if (dbase->put(dbase, &dbkey, &dbdat, 0)) {
@@ -754,7 +794,7 @@ int main(int argc, char **argv)
 		}
 	}
 
-	if (do_load || do_list)
+	if (do_list)
 		goto out;
 
 	pset[0].fd = socket(PF_PACKET, SOCK_DGRAM, 0);
-- 
2.7.0.windows.2