[U-Boot] [PATCH v2 1/1] net: Store waiting packet in a different buffer when making ARP requests

[Joe Hershberger]

On Wed, Jul 4, 2018 at 9:13 PM, Tran Tien Dat
<peter.trantiendat at gmail.com> wrote:
> U-Boot has 1 common buffer to send Ethernet frames, pointed to by
> net_tx_packet.  When sending to an IP address without knowing the MAC
> address, U-Boot makes an ARP request (using the arp_tx_packet buffer) to
> find out the MAC address of the IP addressr. When a matching ARP reply is
> received, U-Boot continues sending the frame stored in the net_tx_packet
> buffer.
>
> However, in the mean time, if U-Boot needs to send out any network packets
> (e.g. replying ping packets or ARP requests for its own IP address etc.),
> it will use the net_tx_packet buffer to prepare the new packet. Thus this
> buffer is no longer the original packet meant to be transmitted after the
> ARP reply. The original packet will be lost.
>
> U-Boot has another buffer, pointed to by arp_tx_packet which is used to
> prepare ARP requests. ARP requests use this buffer instead of the normal
> net_tx_packet in order to avoid modifying the waiting packet to be sent.
> However, this approach does not prevent other parts of the codes from
> modifying the waiting packet to be sent, as explained above. This patch
> repurposes the arp_tx_packet buffer to be used to store the waiting packet
> to be sent, and use the normal net_tx_packet buffer to send ARP request
> instead.
>
> Signed-off-by: Tran Tien Dat <peter.trantiendat at gmail.com>

Seems good, thanks!

Acked-by: Joe Hershberger <joe.hershberger at ni.com>

> ---
>
> Changes in v2:
> - Provide more detailed description
>
>  net/arp.c | 18 ++++++++++--------
>  net/arp.h |  1 +
>  net/net.c |  3 +++
>  3 files changed, 14 insertions(+), 8 deletions(-)
>
> diff --git a/net/arp.c b/net/arp.c
> index b8a71684cd..f5e2c0b0cf 100644
> --- a/net/arp.c
> +++ b/net/arp.c
> @@ -35,8 +35,8 @@ int           arp_wait_tx_packet_size;
>  ulong          arp_wait_timer_start;
>  int            arp_wait_try;
>
> -static uchar   *arp_tx_packet; /* THE ARP transmit packet */
> -static uchar   arp_tx_packet_buf[PKTSIZE_ALIGN + PKTALIGN];
> +uchar   *arp_wait_tx_packet;   /* THE waiting transmit packet after ARP */
> +static uchar   arp_wait_tx_packet_buf[PKTSIZE_ALIGN + PKTALIGN];
>
>  void arp_init(void)
>  {
> @@ -45,8 +45,8 @@ void arp_init(void)
>         net_arp_wait_packet_ip.s_addr = 0;
>         net_arp_wait_reply_ip.s_addr = 0;
>         arp_wait_tx_packet_size = 0;
> -       arp_tx_packet = &arp_tx_packet_buf[0] + (PKTALIGN - 1);
> -       arp_tx_packet -= (ulong)arp_tx_packet % PKTALIGN;
> +       arp_wait_tx_packet = &arp_wait_tx_packet_buf[0] + (PKTALIGN - 1);
> +       arp_wait_tx_packet -= (ulong)arp_wait_tx_packet % PKTALIGN;
>  }
>
>  void arp_raw_request(struct in_addr source_ip, const uchar *target_ethaddr,
> @@ -58,7 +58,7 @@ void arp_raw_request(struct in_addr source_ip, const uchar *target_ethaddr,
>
>         debug_cond(DEBUG_DEV_PKT, "ARP broadcast %d\n", arp_wait_try);
>
> -       pkt = arp_tx_packet;
> +       pkt = net_tx_packet;
>
>         eth_hdr_size = net_set_ether(pkt, net_bcast_ethaddr, PROT_ARP);
>         pkt += eth_hdr_size;
> @@ -76,7 +76,7 @@ void arp_raw_request(struct in_addr source_ip, const uchar *target_ethaddr,
>         memcpy(&arp->ar_tha, target_ethaddr, ARP_HLEN); /* target ET addr */
>         net_write_ip(&arp->ar_tpa, target_ip);          /* target IP addr */
>
> -       net_send_packet(arp_tx_packet, eth_hdr_size + ARP_HDR_SIZE);
> +       net_send_packet(net_tx_packet, eth_hdr_size + ARP_HDR_SIZE);
>  }
>
>  void arp_request(void)
> @@ -217,9 +217,11 @@ void arp_receive(struct ethernet_hdr *et, struct ip_udp_hdr *ip, int len)
>
>                         /* set the mac address in the waiting packet's header
>                            and transmit it */
> -                       memcpy(((struct ethernet_hdr *)net_tx_packet)->et_dest,
> +                       memcpy(((struct ethernet_hdr *)arp_wait_tx_packet)
> +                                       ->et_dest,
>                                &arp->ar_sha, ARP_HLEN);
> -                       net_send_packet(net_tx_packet, arp_wait_tx_packet_size);
> +                       net_send_packet(arp_wait_tx_packet,
> +                                       arp_wait_tx_packet_size);
>
>                         /* no arp request pending now */
>                         net_arp_wait_packet_ip.s_addr = 0;
> diff --git a/net/arp.h b/net/arp.h
> index afb86958f3..65d73927a7 100644
> --- a/net/arp.h
> +++ b/net/arp.h
> @@ -20,6 +20,7 @@ extern uchar *arp_wait_packet_ethaddr;
>  extern int arp_wait_tx_packet_size;
>  extern ulong arp_wait_timer_start;
>  extern int arp_wait_try;
> +extern uchar *arp_wait_tx_packet;
>
>  void arp_init(void);
>  void arp_request(void);
> diff --git a/net/net.c b/net/net.c
> index f35695b4fc..6325ad3e1a 100644
> --- a/net/net.c
> +++ b/net/net.c
> @@ -836,6 +836,9 @@ int net_send_udp_packet(uchar *ether, struct in_addr dest, int dport, int sport,
>
>                 /* size of the waiting packet */
>                 arp_wait_tx_packet_size = pkt_hdr_size + payload_len;
> +               /* copy current packet to ARP waiting packet buffer */
> +               memcpy(arp_wait_tx_packet, net_tx_packet,
> +                      arp_wait_tx_packet_size);
>
>                 /* and do the ARP request */
>                 arp_wait_try = 1;
> --
> 2.18.0
>
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