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Commit 954fba02 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
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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: default avatarBogdan Hamciuc <bogdan.hamciuc@freescale.com>
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Tested-by: default avatarBogdan Hamciuc <bogdan.hamciuc@freescale.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Neil Horman <nhorman@tuxdriver.com>
Reviewed-by: default avatarNeil Horman <nhorman@tuxdriver.com>
Reviewed-by: default avatarCong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: default avatarDavid 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);