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Commit 723b8e46 authored by Tom Herbert's avatar Tom Herbert Committed by David S. Miller
Browse files

udp: In udp_flow_src_port use random hash value if skb_get_hash fails 

In the unlikely event that skb_get_hash is unable to deduce a hash
in udp_flow_src_port we use a consistent random value instead.
This is specified in GRE/UDP draft section 3.2.1:
https://tools.ietf.org/html/draft-ietf-tsvwg-gre-in-udp-encap-04



Signed-off-by: default avatarTom Herbert <therbert@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent fed0a159

include/net/udp.h

+15 −6
Original line number Diff line number Diff line
@@ -194,6 +194,8 @@ int udp_lib_get_port(struct sock *sk, unsigned short snum, 
		     int (*)(const struct sock *, const struct sock *),

		     unsigned int hash2_nulladdr);



u32 udp_flow_hashrnd(void);



static inline __be16 udp_flow_src_port(struct net *net, struct sk_buff *skb,

				       int min, int max, bool use_eth)

{
@@ -205,12 +207,19 @@ static inline __be16 udp_flow_src_port(struct net *net, struct sk_buff *skb, 
	}



	hash = skb_get_hash(skb);

	if (unlikely(!hash) && use_eth) {

		/* Can't find a normal hash, caller has indicated an Ethernet

		 * packet so use that to compute a hash.

	if (unlikely(!hash)) {

		if (use_eth) {

			/* Can't find a normal hash, caller has indicated an

			 * Ethernet packet so use that to compute a hash.

			 */

			hash = jhash(skb->data, 2 * ETH_ALEN,

				     (__force u32) skb->protocol);

		} else {

			/* Can't derive any sort of hash for the packet, set

			 * to some consistent random value.

			 */

			hash = udp_flow_hashrnd();

		}

	}



	/* Since this is being sent on the wire obfuscate hash a bit

net/ipv4/udp.c

+10 −0
Original line number Diff line number Diff line
@@ -2525,6 +2525,16 @@ void __init udp_table_init(struct udp_table *table, const char *name) 
	}

}



u32 udp_flow_hashrnd(void)

{

	static u32 hashrnd __read_mostly;



	net_get_random_once(&hashrnd, sizeof(hashrnd));



	return hashrnd;

}

EXPORT_SYMBOL(udp_flow_hashrnd);



void __init udp_init(void)

{

	unsigned long limit;