[PATCH] powerpc/cell spidernet zlen min packet length

Polite device drivers pad short packets to 60 bytes,
so that mean-spirited users don't accidentally DOS
some other OS that can't handle short packets.

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Cc: James K Lewis <jklewis@us.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

1 files changed, 14 insertions, 4 deletions

diff --git a/drivers/net/spider_net.c b/drivers/net/spider_net.c
index 52bf1b2968b3..f5f73571a7a6 100644
--- a/drivers/net/spider_net.c
+++ b/drivers/net/spider_net.c
@@ -648,18 +648,26 @@ spider_net_prepare_tx_descr(struct spider_net_card *card,
 {
         struct spider_net_descr *descr = card->tx_chain.head;
         dma_addr_t buf;
+        int length;
 
-        buf = pci_map_single(card->pdev, skb->data, skb->len, PCI_DMA_TODEVICE);
+        length = skb->len;
+        if (length < ETH_ZLEN) {
+                if (skb_pad(skb, ETH_ZLEN-length))
+                        return 0;
+                length = ETH_ZLEN;
+        }
+
+        buf = pci_map_single(card->pdev, skb->data, length, PCI_DMA_TODEVICE);
         if (pci_dma_mapping_error(buf)) {
                 if (netif_msg_tx_err(card) && net_ratelimit())
                         pr_err("could not iommu-map packet (%p, %i). "
-                                  "Dropping packet\n", skb->data, skb->len);
+                                  "Dropping packet\n", skb->data, length);
                 card->spider_stats.tx_iommu_map_error++;
                 return -ENOMEM;
         }
 
         descr->buf_addr = buf;
-        descr->buf_size = skb->len;
+        descr->buf_size = length;
         descr->next_descr_addr = 0;
         descr->skb = skb;
         descr->data_status = 0;
@@ -693,6 +701,7 @@ spider_net_release_tx_descr(struct spider_net_card *card)
 {
         struct spider_net_descr *descr = card->tx_chain.tail;
         struct sk_buff *skb;
+        unsigned int len;
 
         card->tx_chain.tail = card->tx_chain.tail->next;
         descr->dmac_cmd_status |= SPIDER_NET_DESCR_NOT_IN_USE;
@@ -701,7 +710,8 @@ spider_net_release_tx_descr(struct spider_net_card *card)
         skb = descr->skb;
         if (!skb)
                 return;
-        pci_unmap_single(card->pdev, descr->buf_addr, skb->len,
+        len = skb->len < ETH_ZLEN ? ETH_ZLEN : skb->len;
+        pci_unmap_single(card->pdev, descr->buf_addr, len,
                         PCI_DMA_TODEVICE);
         dev_kfree_skb_any(skb);
 }