[PATCH net v2] net: ipv4: Fix rtnexthop len when RTA_FLOW is present

[PATCH net v2] net: ipv4: Fix rtnexthop len when RTA_FLOW is present

[Xiao Liang]

Multipath RTA_FLOW is embedded in nexthop. Dump it in fib_add_nexthop()
to get the length of rtnexthop correct.

Fixes: b0f60193632e ("ipv4: Refactor nexthop attributes in fib_dump_info")
Signed-off-by: Xiao Liang <shaw.leon@gmail.com>
---
 include/net/ip_fib.h     |  2 +-
 include/net/nexthop.h    |  2 +-
 net/ipv4/fib_semantics.c | 15 ++++++++-------
 net/ipv6/route.c         |  5 +++--
 4 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/include/net/ip_fib.h b/include/net/ip_fib.h
index 21c5386d4a6d..ab5348e57db1 100644
--- a/include/net/ip_fib.h
+++ b/include/net/ip_fib.h
@@ -597,5 +597,5 @@ int ip_valid_fib_dump_req(struct net *net, const struct nlmsghdr *nlh,
 int fib_nexthop_info(struct sk_buff *skb, const struct fib_nh_common *nh,
 		     u8 rt_family, unsigned char *flags, bool skip_oif);
 int fib_add_nexthop(struct sk_buff *skb, const struct fib_nh_common *nh,
-		    int nh_weight, u8 rt_family);
+		    int nh_weight, u8 rt_family, u32 nh_tclassid);
 #endif  /* _NET_FIB_H */
diff --git a/include/net/nexthop.h b/include/net/nexthop.h
index 10e1777877e6..28085b995ddc 100644
--- a/include/net/nexthop.h
+++ b/include/net/nexthop.h
@@ -325,7 +325,7 @@ int nexthop_mpath_fill_node(struct sk_buff *skb, struct nexthop *nh,
 		struct fib_nh_common *nhc = &nhi->fib_nhc;
 		int weight = nhg->nh_entries[i].weight;
 
-		if (fib_add_nexthop(skb, nhc, weight, rt_family) < 0)
+		if (fib_add_nexthop(skb, nhc, weight, rt_family, 0) < 0)
 			return -EMSGSIZE;
 	}
 
diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index b42c429cebbe..e9818faaff4d 100644
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -1661,7 +1661,7 @@ EXPORT_SYMBOL_GPL(fib_nexthop_info);
 
 #if IS_ENABLED(CONFIG_IP_ROUTE_MULTIPATH) || IS_ENABLED(CONFIG_IPV6)
 int fib_add_nexthop(struct sk_buff *skb, const struct fib_nh_common *nhc,
-		    int nh_weight, u8 rt_family)
+		    int nh_weight, u8 rt_family, u32 nh_tclassid)
 {
 	const struct net_device *dev = nhc->nhc_dev;
 	struct rtnexthop *rtnh;
@@ -1679,6 +1679,12 @@ int fib_add_nexthop(struct sk_buff *skb, const struct fib_nh_common *nhc,
 
 	rtnh->rtnh_flags = flags;
 
+#ifdef CONFIG_IP_ROUTE_CLASSID
+	if (nh_tclassid &&
+	    nla_put_u32(skb, RTA_FLOW, nh_tclassid))
+		goto nla_put_failure;
+#endif
+
 	/* length of rtnetlink header + attributes */
 	rtnh->rtnh_len = nlmsg_get_pos(skb) - (void *)rtnh;
 
@@ -1707,13 +1713,8 @@ static int fib_add_multipath(struct sk_buff *skb, struct fib_info *fi)
 
 	for_nexthops(fi) {
 		if (fib_add_nexthop(skb, &nh->nh_common, nh->fib_nh_weight,
-				    AF_INET) < 0)
+				    AF_INET, nh->nh_tclassid) < 0)
 			goto nla_put_failure;
-#ifdef CONFIG_IP_ROUTE_CLASSID
-		if (nh->nh_tclassid &&
-		    nla_put_u32(skb, RTA_FLOW, nh->nh_tclassid))
-			goto nla_put_failure;
-#endif
 	} endfor_nexthops(fi);
 
 mp_end:
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index dbc224023977..9b9ef09382ab 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -5681,14 +5681,15 @@ static int rt6_fill_node(struct net *net, struct sk_buff *skb,
 			goto nla_put_failure;
 
 		if (fib_add_nexthop(skb, &rt->fib6_nh->nh_common,
-				    rt->fib6_nh->fib_nh_weight, AF_INET6) < 0)
+				    rt->fib6_nh->fib_nh_weight, AF_INET6,
+				    0) < 0)
 			goto nla_put_failure;
 
 		list_for_each_entry_safe(sibling, next_sibling,
 					 &rt->fib6_siblings, fib6_siblings) {
 			if (fib_add_nexthop(skb, &sibling->fib6_nh->nh_common,
 					    sibling->fib6_nh->fib_nh_weight,
-					    AF_INET6) < 0)
+					    AF_INET6, 0) < 0)
 				goto nla_put_failure;
 		}
 
-- 
2.33.0

Re: [PATCH net v2] net: ipv4: Fix rtnexthop len when RTA_FLOW is present

[David Ahern]

On 9/23/21 1:22 AM, Xiao Liang wrote:
> diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
> index b42c429cebbe..e9818faaff4d 100644
> --- a/net/ipv4/fib_semantics.c
> +++ b/net/ipv4/fib_semantics.c
> @@ -1661,7 +1661,7 @@ EXPORT_SYMBOL_GPL(fib_nexthop_info);
>  
>  #if IS_ENABLED(CONFIG_IP_ROUTE_MULTIPATH) || IS_ENABLED(CONFIG_IPV6)
>  int fib_add_nexthop(struct sk_buff *skb, const struct fib_nh_common *nhc,
> -		    int nh_weight, u8 rt_family)
> +		    int nh_weight, u8 rt_family, u32 nh_tclassid)
>  {
>  	const struct net_device *dev = nhc->nhc_dev;
>  	struct rtnexthop *rtnh;
> @@ -1679,6 +1679,12 @@ int fib_add_nexthop(struct sk_buff *skb, const struct fib_nh_common *nhc,
>  
>  	rtnh->rtnh_flags = flags;
>  
> +#ifdef CONFIG_IP_ROUTE_CLASSID
> +	if (nh_tclassid &&
> +	    nla_put_u32(skb, RTA_FLOW, nh_tclassid))
> +		goto nla_put_failure;
> +#endif

I think we can drop the ifdef here if 0 is always passed when the CONFIG
is not enabled.

> +
>  	/* length of rtnetlink header + attributes */
>  	rtnh->rtnh_len = nlmsg_get_pos(skb) - (void *)rtnh;
>  
> @@ -1707,13 +1713,8 @@ static int fib_add_multipath(struct sk_buff *skb, struct fib_info *fi)
>  
>  	for_nexthops(fi) {
>  		if (fib_add_nexthop(skb, &nh->nh_common, nh->fib_nh_weight,
> -				    AF_INET) < 0)
> +				    AF_INET, nh->nh_tclassid) < 0)

This will fail to compile if the CONFIG is not enabled. Use a temp variable:
		__u32 nh_tclassid = 0;

#ifdef CONFIG_IP_ROUTE_CLASSID
        	nh_tclassid = nh->nh_tclassid
#endif

then pass that to fib_add_nexthop

>  			goto nla_put_failure;
> -#ifdef CONFIG_IP_ROUTE_CLASSID
> -		if (nh->nh_tclassid &&
> -		    nla_put_u32(skb, RTA_FLOW, nh->nh_tclassid))
> -			goto nla_put_failure;
> -#endif
>  	} endfor_nexthops(fi);
>  
>  mp_end: