netdev - Re: IP oversized ip oacket from - header size should be skipped?

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Date: Fri, 28 Jun 2024 12:53:43 +0200
From: Florian Westphal <fw@...len.de>
To: Ian Kumlien <ian.kumlien@...il.com>
Cc: Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: IP oversized ip oacket from - header size should be skipped?

Ian Kumlien <ian.kumlien@...il.com> wrote:
> Hi,
> 
> In net/ipv4/ip_fragment.c line 412:
> static int ip_frag_reasm(struct ipq *qp, struct sk_buff *skb,
>                          struct sk_buff *prev_tail, struct net_device *dev)
> {
> ...
>         len = ip_hdrlen(skb) + qp->q.len;
>         err = -E2BIG;
>         if (len > 65535)
>                 goto out_oversize;
> ....
> 
> We can expand the expression to:
> len = (ip_hdr(skb)->ihl * 4) + qp->q.len;
> 
> But it's still weird since the definition of q->len is: "total length
> of the original datagram"

AFAICS datagram == l4 payload, so adding ihl is correct.