igb: Pull timestamp from fragment before adding it to skb

This change makes it so that we pull the timestamp from the fragment before
we add it to the skb.  By doing this we can avoid a possible issue in which
the fragment can possibly be less than IGB_RX_HDR_LEN due to the timestamp
being pulled after the copybreak check.

While making this change I realized we could also pull the rest of the
igb_pull_tail function into igb_add_rx_frag since in the case of igb,
unlike ixgbe, we are able to unmap the entire buffer before calling
add_rx_frag so merging the two allows for sharing of code between the two
merged functions.
Reported-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Alexander Duyck <alexander.h.duyck@redhat.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/igb/igb_main.c

@@ -6621,22 +6621,25 @@ static bool igb_add_rx_frag(struct igb_ring *rx_ring,
 			    struct sk_buff *skb)
 {
 	struct page *page = rx_buffer->page;
+	unsigned char *va = page_address(page) + rx_buffer->page_offset;
 	unsigned int size = le16_to_cpu(rx_desc->wb.upper.length);
 #if (PAGE_SIZE < 8192)
 	unsigned int truesize = IGB_RX_BUFSZ;
 #else
-	unsigned int truesize = ALIGN(size, L1_CACHE_BYTES);
+	unsigned int truesize = SKB_DATA_ALIGN(size);
 #endif
+	unsigned int pull_len;
 
-	if ((size <= IGB_RX_HDR_LEN) && !skb_is_nonlinear(skb)) {
-		unsigned char *va = page_address(page) + rx_buffer->page_offset;
+	if (unlikely(skb_is_nonlinear(skb)))
+		goto add_tail_frag;
 
-		if (igb_test_staterr(rx_desc, E1000_RXDADV_STAT_TSIP)) {
-			igb_ptp_rx_pktstamp(rx_ring->q_vector, va, skb);
-			va += IGB_TS_HDR_LEN;
-			size -= IGB_TS_HDR_LEN;
-		}
+	if (unlikely(igb_test_staterr(rx_desc, E1000_RXDADV_STAT_TSIP))) {
+		igb_ptp_rx_pktstamp(rx_ring->q_vector, va, skb);
+		va += IGB_TS_HDR_LEN;
+		size -= IGB_TS_HDR_LEN;
+	}
 
+	if (likely(size <= IGB_RX_HDR_LEN)) {
 		memcpy(__skb_put(skb, size), va, ALIGN(size, sizeof(long)));
 
 		/* page is not reserved, we can reuse buffer as-is */
@@ -6648,8 +6651,21 @@ static bool igb_add_rx_frag(struct igb_ring *rx_ring,
 		return false;
 	}
 
+	/* we need the header to contain the greater of either ETH_HLEN or
+	 * 60 bytes if the skb->len is less than 60 for skb_pad.
+	 */
+	pull_len = eth_get_headlen(va, IGB_RX_HDR_LEN);
+
+	/* align pull length to size of long to optimize memcpy performance */
+	memcpy(__skb_put(skb, pull_len), va, ALIGN(pull_len, sizeof(long)));
+
+	/* update all of the pointers */
+	va += pull_len;
+	size -= pull_len;
+
+add_tail_frag:
 	skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags, page,
-			rx_buffer->page_offset, size, truesize);
+			(unsigned long)va & ~PAGE_MASK, size, truesize);
 
 	return igb_can_reuse_rx_page(rx_buffer, page, truesize);
 }
@@ -6790,62 +6806,6 @@ static bool igb_is_non_eop(struct igb_ring *rx_ring,
 	return true;
 }
 
-/**
- *  igb_pull_tail - igb specific version of skb_pull_tail
- *  @rx_ring: rx descriptor ring packet is being transacted on
- *  @rx_desc: pointer to the EOP Rx descriptor
- *  @skb: pointer to current skb being adjusted
- *
- *  This function is an igb specific version of __pskb_pull_tail.  The
- *  main difference between this version and the original function is that
- *  this function can make several assumptions about the state of things
- *  that allow for significant optimizations versus the standard function.
- *  As a result we can do things like drop a frag and maintain an accurate
- *  truesize for the skb.
- */
-static void igb_pull_tail(struct igb_ring *rx_ring,
-			  union e1000_adv_rx_desc *rx_desc,
-			  struct sk_buff *skb)
-{
-	struct skb_frag_struct *frag = &skb_shinfo(skb)->frags[0];
-	unsigned char *va;
-	unsigned int pull_len;
-
-	/* it is valid to use page_address instead of kmap since we are
-	 * working with pages allocated out of the lomem pool per
-	 * alloc_page(GFP_ATOMIC)
-	 */
-	va = skb_frag_address(frag);
-
-	if (igb_test_staterr(rx_desc, E1000_RXDADV_STAT_TSIP)) {
-		/* retrieve timestamp from buffer */
-		igb_ptp_rx_pktstamp(rx_ring->q_vector, va, skb);
-
-		/* update pointers to remove timestamp header */
-		skb_frag_size_sub(frag, IGB_TS_HDR_LEN);
-		frag->page_offset += IGB_TS_HDR_LEN;
-		skb->data_len -= IGB_TS_HDR_LEN;
-		skb->len -= IGB_TS_HDR_LEN;
-
-		/* move va to start of packet data */
-		va += IGB_TS_HDR_LEN;
-	}
-
-	/* we need the header to contain the greater of either ETH_HLEN or
-	 * 60 bytes if the skb->len is less than 60 for skb_pad.
-	 */
-	pull_len = eth_get_headlen(va, IGB_RX_HDR_LEN);
-
-	/* align pull length to size of long to optimize memcpy performance */
-	skb_copy_to_linear_data(skb, va, ALIGN(pull_len, sizeof(long)));
-
-	/* update all of the pointers */
-	skb_frag_size_sub(frag, pull_len);
-	frag->page_offset += pull_len;
-	skb->data_len -= pull_len;
-	skb->tail += pull_len;
-}
-
 /**
  *  igb_cleanup_headers - Correct corrupted or empty headers
  *  @rx_ring: rx descriptor ring packet is being transacted on
@@ -6873,10 +6833,6 @@ static bool igb_cleanup_headers(struct igb_ring *rx_ring,
 		}
 	}
 
-	/* place header in linear portion of buffer */
-	if (skb_is_nonlinear(skb))
-		igb_pull_tail(rx_ring, rx_desc, skb);
-
 	/* if eth_skb_pad returns an error the skb was freed */
 	if (eth_skb_pad(skb))
 		return true;