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Date: Mon, 28 Apr 2008 12:13:27 +0000
From: Kostya B <bkostya@...mail.com>
To: <netdev@...r.kernel.org>
Subject: [PATCH][IPv4] UFO: prevent generation of chained skb
[IPv4] UFO: prevent generation of chained skb destined to UFO device
Problem:
ip_append_data() could wrongly generate a chained skb for devices which support UFO.
When sk_write_queue is not empty (e.g. MSG_MORE), __instead__ of appending data
into the next nr_frag of the queued skb, a new chained skb is created.
I would normally assume UFO device should get data in nr_frags and not in frag_list.
Later the udp4_hwcsum_outgoing() resets csum to NONE and skb_gso_segment() has oops.
Proposal:
1. Even length is less than mtu, employ ip_ufo_append_data() and append data to the __existed__ skb in the sk_write_queue.
2. ip_ufo_append_data() is fixed due to a wrong manipulation of peek-ing and later enqueue-ing of the same skb.
Now, enqueuing is always performed, because on error the further ip_flush_pending_frames() would release the queued skb.
Signed-off-by: Kostya B
---
net/ipv4/ip_output.c | 25 +++++++++----------------
1 file changed, 9 insertions(+), 16 deletions(-)
diff -uprN -X linux-2.6.25-git11/Documentation/dontdiff linux-2.6.25-git11/net/ipv4/ip_output.c linux-2.6.25-git11-fix/net/ipv4/ip_output.c
--- linux-2.6.25-git11/net/ipv4/ip_output.c 2008-04-28 12:22:00.000000000 +0300
+++ linux-2.6.25-git11-fix/net/ipv4/ip_output.c 2008-04-28 14:02:41.000000000 +0300
@@ -753,23 +753,15 @@ static inline int ip_ufo_append_data(str
skb->ip_summed = CHECKSUM_PARTIAL;
skb->csum = 0;
sk->sk_sndmsg_off = 0;
+
+ /* specify the length of each IP datagram fragment*/
+ skb_shinfo(skb)->gso_size = mtu - fragheaderlen;
+ skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
+ __skb_queue_tail(&sk->sk_write_queue, skb);
}
- err = skb_append_datato_frags(sk,skb, getfrag, from,
+ return skb_append_datato_frags(sk,skb, getfrag, from,
(length - transhdrlen));
- if (!err) {
- /* specify the length of each IP datagram fragment*/
- skb_shinfo(skb)->gso_size = mtu - fragheaderlen;
- skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
- __skb_queue_tail(&sk->sk_write_queue, skb);
-
- return 0;
- }
- /* There is not enough support do UFO ,
- * so follow normal path
- */
- kfree_skb(skb);
- return err;
}
/*
@@ -863,8 +855,9 @@ int ip_append_data(struct sock *sk,
csummode = CHECKSUM_PARTIAL;
inet->cork.length += length;
- if (((length> mtu) && (sk->sk_protocol == IPPROTO_UDP)) &&
- (rt->u.dst.dev->features & NETIF_F_UFO)) {
+ if (((length> mtu) || !skb_queue_empty(&sk->sk_write_queue)) &&
+ (sk->sk_protocol == IPPROTO_UDP) &&
+ (rt->u.dst.dev->features & NETIF_F_UFO)) {
err = ip_ufo_append_data(sk, getfrag, from, length, hh_len,
fragheaderlen, transhdrlen, mtu,
---
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