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Message-ID: <1424482561.5565.34.camel@edumazet-glaptop2.roam.corp.google.com> Date: Fri, 20 Feb 2015 17:36:01 -0800 From: Eric Dumazet <eric.dumazet@...il.com> To: Tom Herbert <therbert@...gle.com> Cc: davem@...emloft.net, netdev@...r.kernel.org Subject: Re: [PATCH net-next] net: Eliminate txhash in sock and reflect RX hash on transmit On Fri, 2015-02-20 at 16:24 -0800, Tom Herbert wrote: > Instead of having a separate hash value in sock structure for transmit > and receive, we can use the rxhash value for both and eliminate the > txhash value. This simplifies the code and reflects the receive hash a > device provides to the stack for packets transmitted on the associated > connection. The hash value returned by a device could have meaning when > used in transmit to identify a flow, for instance the hash may be a flow > key for a flow created in a (virtual) device. With the flow key provided > on transmit this can obviate the need to create the hash and do the > lookup on the fly in transmit. > +static inline void sock_init_rxhash(struct sock *sk) > +{ > + get_random_bytes(&sk->sk_rxhash, sizeof(u32)); > } Wow. You just depleted entropy pool completely. prandom_bytes() or prandom_u32() will just be fine. Quite frankly, all these changes seem pointless, as you have no guarantee same hash will be used for packets of a given flow. Obviously the outgoing SYN packet has no easy way to know what will be the rxhash in opposite direction. I think I already mentioned this problem. So whats the point ? -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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