From d2fd204b0ae35512a04702e480bb0d16878e98be Mon Sep 17 00:00:00 2001
From: Paul Komkoff <i@stingr.net>
Date: Mon, 4 Jan 2021 18:13:28 +0400
Subject: [PATCH 1/2] core: work around interface enum buffer overrun

When a system has too many interfaces and too many addresses,
8 kilobytes isn't enough to fit all of the netlink responses.
As the result, kamailio gets stuck in a loop where it tries
to do a 0-length recv.

Increase the buffer to 32K. It's a miniscule amount for modern
times anyway. Also, add diagnostics to make further troubleshooting
easier.

Proper fix would be to switch to libnl here, which would make a
good weekend project.
---
 src/core/socket_info.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/src/core/socket_info.c b/src/core/socket_info.c
index a46aba24ad6..d34f3fb4cd6 100644
--- a/src/core/socket_info.c
+++ b/src/core/socket_info.c
@@ -1070,6 +1070,7 @@ static int nl_bound_sock(void)
 	req.g.rtgen_family = family;\
 	} while(0);
 
+#define NETLINK_BUFFER_SIZE 32768
 	
 static int get_flags(int family){
 	struct {
@@ -1079,7 +1080,7 @@ static int get_flags(int family){
 	int rtn = 0;
 	struct nlmsghdr*  nlp;
 	struct ifinfomsg *ifi;
-	char buf[8192];
+	char buf[NETLINK_BUFFER_SIZE];
 	char *p = buf;
 	int nll = 0;
     int nl_sock = -1;
@@ -1095,6 +1096,10 @@ static int get_flags(int family){
 	}
 
 	while(1) {
+		if ((sizeof(buf) - nll) == 0) {
+			LM_ERR("netlink buffer overflow in get_flags");
+			goto error;
+		}
 		rtn = recv(nl_sock, p, sizeof(buf) - nll, 0);
 		nlp = (struct nlmsghdr *) p;
 		if(nlp->nlmsg_type == NLMSG_DONE){
@@ -1148,7 +1153,7 @@ static int build_iface_list(void)
 	struct nlmsghdr*  nlp;
 	struct ifaddrmsg *ifi;
 	int rtl;
-	char buf[8192];
+	char buf[NETLINK_BUFFER_SIZE];
 	char *p = buf;
 	int nll = 0;
 	struct rtattr * rtap;
@@ -1184,6 +1189,10 @@ static int build_iface_list(void)
 		nll = 0;
 		p = buf;
 		while(1) {
+			if ((sizeof(buf) - nll) == 0) {
+				LM_ERR("netlink buffer overflow in build_iface_list");
+				goto error;
+			}
 			rtn = recv(nl_sock, p, sizeof(buf) - nll, 0);
 			LM_DBG("received %d byles \n", rtn);
 			nlp = (struct nlmsghdr *) p;

From 42f7702430c312b2c9caea8f617af4e3719ef12f Mon Sep 17 00:00:00 2001
From: Paul Komkoff <i@stingr.net>
Date: Mon, 4 Jan 2021 18:18:01 +0400
Subject: [PATCH 2/2] core: fix unused argument in socket_info.c:get_flags

get_flags has an argument - family - which is supposed to be used
in netlink message, otherwise why would we need it?
---
 src/core/socket_info.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/core/socket_info.c b/src/core/socket_info.c
index d34f3fb4cd6..d55f506bcc5 100644
--- a/src/core/socket_info.c
+++ b/src/core/socket_info.c
@@ -1085,7 +1085,7 @@ static int get_flags(int family){
 	int nll = 0;
     int nl_sock = -1;
 
-	fill_nl_req(req, RTM_GETLINK, AF_INET);
+	fill_nl_req(req, RTM_GETLINK, family);
 
 	if((nl_sock = nl_bound_sock()) < 0) return -1;