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Message-ID: <1285785794.2813.292.camel@edumazet-laptop> Date: Wed, 29 Sep 2010 20:43:14 +0200 From: Eric Dumazet <eric.dumazet@...il.com> To: Jesse Gross <jesse@...ira.com> Cc: David Miller <davem@...emloft.net>, netdev <netdev@...r.kernel.org> Subject: Re: [PATCH net-next-2.6] ip_gre: lockless xmit Le mercredi 29 septembre 2010 à 10:33 -0700, Jesse Gross a écrit : > The tx lock has another use here: to break local loops. With this > change, a misconfigured tunnel can bring down the machine with a stack > overflow. There are clearly other ways to fix this that don't require > a lock that restricts parallelism, such as a loop counter, but that's > the way it is now. Thats a very good point ! We could use a loop counter in the skb, but this use a bit of ram, or percpu counters in tunnel drivers, to avoid a given level of recursion. /* this should be shared by all tunnels */ DEFINE_PER_CPU(tunnel_xmit_count); tunnel_xmit() { if (__this_cpu_read(tunnel_xmit_count) >= LIMIT) goto tx_error; __this_cpu_inc(tunnel_xmit_count); .... __IPTUNNEL_XMIT(tstats, &dev->stats); __this_cpu_dec(tunnel_xmit_count), return NETDEV_TX_OK; } -- 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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