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Date: Fri, 7 Mar 2014 16:09:14 -0800
From: Vincent Li <vincent.mc.li@...il.com>
To: "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: is printk proper tool to trace code path in net code ?
Hi,
I am still trying to trace a potential kernel bug selecting wrong
source ip 127.0.0.1 when there is route proper route table in kernel
on centos 2.6.32 based kernel
http://www.spinics.net/lists/netdev/msg271050.html
and here I am trying to use printk to understand a code path of
kernel selecting source ip logic
I am only doing printk when the destination ip matches my input ip
'myip', I want to know if I am doing something stupid that could crash
kernel, cause I did see get a kernel panic when I put printk in
ip_route_output_slow() routine during reboot. but only see once so
far.
[root@...cent-centos64 kernel]# git diff net/ipv4/tcp_ipv4.c
diff --git a/kernel/net/ipv4/tcp_ipv4.c b/kernel/net/ipv4/tcp_ipv4.c
index f43a3b3..8f41d46 100644
--- a/kernel/net/ipv4/tcp_ipv4.c
+++ b/kernel/net/ipv4/tcp_ipv4.c
@@ -152,6 +152,7 @@ int tcp_v4_connect(struct sock *sk, struct
sockaddr *uaddr, int addr_len)
__be32 daddr, nexthop;
int tmp;
int err;
+ u32 myip = 167921763;
if (addr_len < sizeof(struct sockaddr_in))
return -EINVAL;
@@ -166,6 +167,14 @@ int tcp_v4_connect(struct sock *sk, struct
sockaddr *uaddr, int addr_len)
nexthop = inet->opt->faddr;
}
+ if (ntohl(nexthop) == myip ) {
+ printk(KERN_INFO "%s:%d - %s() (%pI4, %d)->(%pI4, %d)\n",
+ __FILE__, __LINE__, __FUNCTION__,
+ &inet->saddr, ntohs(inet->sport),
+ &nexthop, ntohs(usin->sin_port));
+ }
+
+
tmp = ip_route_connect(&rt, nexthop, inet->saddr,
RT_CONN_FLAGS(sk), sk->sk_bound_dev_if,
IPPROTO_TCP,
@@ -230,6 +239,13 @@ int tcp_v4_connect(struct sock *sk, struct
sockaddr *uaddr, int addr_len)
if (err)
goto failure;
+ if (ntohl(inet->daddr) == myip ) {
+ printk(KERN_INFO "%s:%d - %s() (%pI4, %d)->(%pI4, %d)\n",
+ __FILE__, __LINE__, __FUNCTION__,
+ &inet->saddr, ntohs(inet->sport),
+ &inet->daddr, ntohs(inet->dport));
+ }
+
err = ip_route_newports(&rt, IPPROTO_TCP,
inet->sport, inet->dport, sk);
if (err)
[root@...cent-centos64 kernel]# git diff include/net/route.h
diff --git a/kernel/include/net/route.h b/kernel/include/net/route.h
index f494b24..85ef3e5 100644
--- a/kernel/include/net/route.h
+++ b/kernel/include/net/route.h
@@ -161,6 +161,7 @@ static inline int ip_route_connect(struct rtable
**rp, __be32 dst,
int err;
struct net *net = sock_net(sk);
+ u32 myip = 167921763;
if (inet_sk(sk)->transparent)
fl.flags |= FLOWI_FLAG_ANYSRC;
@@ -174,6 +175,14 @@ static inline int ip_route_connect(struct rtable
**rp, __be32 dst,
ip_rt_put(*rp);
*rp = NULL;
}
+ if (ntohl(fl.fl4_dst) == myip ) {
+
+ printk(KERN_INFO "%s:%d - %s() (%pI4, %d)->(%pI4, %d)\n",
+ __FILE__, __LINE__, __FUNCTION__,
+ &fl.fl4_src, ntohs(fl.fl_ip_sport),
+ &fl.fl4_dst, ntohs(fl.fl_ip_dport));
+ }
+
security_sk_classify_flow(sk, &fl);
return ip_route_output_flow(net, rp, &fl, sk, flags);
}
[root@...cent-centos64 kernel]# git diff net/ipv4/route.c
diff --git a/kernel/net/ipv4/route.c b/kernel/net/ipv4/route.c
index 5eef4e1..721b54d 100644
--- a/kernel/net/ipv4/route.c
+++ b/kernel/net/ipv4/route.c
@@ -2494,6 +2494,7 @@ static int ip_route_output_slow(struct net *net,
struct rtable **rp,
int free_res = 0;
int err;
+ printk(KERN_INFO "%s:%d - %s() ", __FILE__, __LINE__, __FUNCTION__);
res.fi = NULL;
#ifdef CONFIG_IP_MULTIPLE_TABLES
@@ -2679,6 +2680,7 @@ int __ip_route_output_key(struct net *net,
struct rtable **rp,
{
unsigned hash;
struct rtable *rth;
+ u32 myip = 167921763;
if (!rt_caching(net))
goto slow_output;
@@ -2701,6 +2703,16 @@ int __ip_route_output_key(struct net *net,
struct rtable **rp,
RT_CACHE_STAT_INC(out_hit);
rcu_read_unlock_bh();
*rp = rth;
+ if (ntohl((*rp)->rt_dst) == myip ) {
+ printk(KERN_INFO "%s:%d - %s() (%pI4,
%d)->(%pI4, %d) dev %s oif %d\n",
+ __FILE__, __LINE__, __FUNCTION__,
+ &(*rp)->rt_src,
ntohs((*rp)->fl.fl_ip_sport),
+ &(*rp)->rt_dst,
ntohs((*rp)->fl.fl_ip_dport),
+ //&(*rp)->rt_dst,
ntohs(flp->fl_ip_dport),
+ (*rp)->u.dst.dev->name, flp->oif
+ );
+ }
+
return 0;
}
RT_CACHE_STAT_INC(out_hlist_search);
[root@...cent-centos64 kernel]# git diff net/ipv4/devinet.c
diff --git a/kernel/net/ipv4/devinet.c b/kernel/net/ipv4/devinet.c
index f84f6dd..f9963e3 100644
--- a/kernel/net/ipv4/devinet.c
+++ b/kernel/net/ipv4/devinet.c
@@ -859,12 +859,21 @@ __be32 inet_select_addr(const struct net_device
*dev, __be32 dst, int scope)
__be32 addr = 0;
struct in_device *in_dev;
struct net *net = dev_net(dev);
+ u32 myip = 167921763;
rcu_read_lock();
in_dev = __in_dev_get_rcu(dev);
+
if (!in_dev)
goto no_in_dev;
+ if (ntohl(dst) == myip ) {
+ printk(KERN_INFO "%s:%d - %s() in_dev %s, dst %pI4\n",
+ __FILE__, __LINE__, __FUNCTION__,
+ in_dev->dev->name, &dst
+ );
+ }
+
for_primary_ifa(in_dev) {
if (ifa->ifa_scope > scope)
continue;
--
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