Commit 954fba02 authored Jun 12, 2012 by Eric Dumazet Committed by David S. Miller Jun 13, 2012

netpoll: fix netpoll_send_udp() bugs



Bogdan Hamciuc diagnosed and fixed following bug in netpoll_send_udp() :

"skb->len += len;" instead of "skb_put(skb, len);"

Meaning that _if_ a network driver needs to call skb_realloc_headroom(),
only packet headers would be copied, leaving garbage in the payload.

However the skb_realloc_headroom() must be avoided as much as possible
since it requires memory and netpoll tries hard to work even if memory
is exhausted (using a pool of preallocated skbs)

It appears netpoll_send_udp() reserved 16 bytes for the ethernet header,
which happens to work for typicall drivers but not all.

Right thing is to use LL_RESERVED_SPACE(dev)
(And also add dev->needed_tailroom of tailroom)

This patch combines both fixes.

Many thanks to Bogdan for raising this issue.

Reported-by: Bogdan Hamciuc <bogdan.hamciuc@freescale.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Tested-by: Bogdan Hamciuc <bogdan.hamciuc@freescale.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Neil Horman <nhorman@tuxdriver.com>
Reviewed-by: Neil Horman <nhorman@tuxdriver.com>
Reviewed-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 5ee31c68

net/core/netpoll.c

+6 −5

Original line number	Diff line number	Diff line
		@@ -362,22 +362,23 @@ EXPORT_SYMBOL(netpoll_send_skb_on_dev);

		void netpoll_send_udp(struct netpoll np, const char msg, int len)
		{
		int total_len, eth_len, ip_len, udp_len;
		int total_len, ip_len, udp_len;
		struct sk_buff *skb;
		struct udphdr *udph;
		struct iphdr *iph;
		struct ethhdr *eth;

		udp_len = len + sizeof(*udph);
		ip_len = eth_len = udp_len + sizeof(*iph);
		total_len = eth_len + ETH_HLEN + NET_IP_ALIGN;
		ip_len = udp_len + sizeof(*iph);
		total_len = ip_len + LL_RESERVED_SPACE(np->dev);

		skb = find_skb(np, total_len, total_len - len);
		skb = find_skb(np, total_len + np->dev->needed_tailroom,
		total_len - len);
		if (!skb)
		return;

		skb_copy_to_linear_data(skb, msg, len);
		skb->len += len;
		skb_put(skb, len);

		skb_push(skb, sizeof(*udph));
		skb_reset_transport_header(skb);

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