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Re: [Qemu-devel] [PATCH] [slirp] Make ARP replies at least 64 bytes long
From: |
Edgar E. Iglesias |
Subject: |
Re: [Qemu-devel] [PATCH] [slirp] Make ARP replies at least 64 bytes long |
Date: |
Wed, 15 Sep 2010 00:22:57 +0200 |
User-agent: |
Mutt/1.5.20 (2009-06-14) |
On Mon, Sep 13, 2010 at 11:02:42PM +0200, Hervé Poussineau wrote:
> IEEE 802.3 standard requires Ethernet frames to be at least 64 bytes long.
> If it is not the case, they will be considered as runt frames, and may be
> ignored by netcard and/or OS
>
> Signed-off-by: Hervé Poussineau <address@hidden>
> ---
> slirp/slirp.c | 12 ++++++++----
> 1 files changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/slirp/slirp.c b/slirp/slirp.c
> index 82fd9b4..2e8c017 100644
> --- a/slirp/slirp.c
> +++ b/slirp/slirp.c
> @@ -599,9 +599,12 @@ static void arp_input(Slirp *slirp, const uint8_t *pkt,
> int pkt_len)
> {
> struct ethhdr *eh = (struct ethhdr *)pkt;
> struct arphdr *ah = (struct arphdr *)(pkt + ETH_HLEN);
> - uint8_t arp_reply[ETH_HLEN + sizeof(struct arphdr)];
> - struct ethhdr *reh = (struct ethhdr *)arp_reply;
> - struct arphdr *rah = (struct arphdr *)(arp_reply + ETH_HLEN);
> + union {
> + uint8_t data[ETH_HLEN + sizeof(struct arphdr)];
> + uint8_t payload[64]; /* Minimum Ethernet frame size */
> + } arp_reply;
> + struct ethhdr *reh = (struct ethhdr *)arp_reply.data;
> + struct arphdr *rah = (struct arphdr *)(arp_reply.data + ETH_HLEN);
Hi,
Would you mind explaning the point of the union here? Why not just
do something like:
- uint8_t arp_reply[ETH_HLEN + sizeof(struct arphdr)];
+ uint8_t arp_reply[MAX(ETH_HLEN + sizeof(struct arphdr), 64)];
Cheers
> int ar_op;
> struct ex_list *ex_ptr;
>
> @@ -619,6 +622,7 @@ static void arp_input(Slirp *slirp, const uint8_t *pkt,
> int pkt_len)
> }
> return;
> arp_ok:
> + memset(&arp_reply, 0, sizeof(arp_reply));
> /* XXX: make an ARP request to have the client address */
> memcpy(slirp->client_ethaddr, eh->h_source, ETH_ALEN);
>
> @@ -637,7 +641,7 @@ static void arp_input(Slirp *slirp, const uint8_t *pkt,
> int pkt_len)
> rah->ar_sip = ah->ar_tip;
> memcpy(rah->ar_tha, ah->ar_sha, ETH_ALEN);
> rah->ar_tip = ah->ar_sip;
> - slirp_output(slirp->opaque, arp_reply, sizeof(arp_reply));
> + slirp_output(slirp->opaque, (const uint8_t *)&arp_reply,
> sizeof(arp_reply));
> }
> break;
> case ARPOP_REPLY:
> --
> 1.7.1.GIT
>
>