[SCTP]: Don't do CRC32C checksum over loopback.

Signed-off-by: Sridhar Samudrala <sri@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sctp/input.c

@@ -141,7 +141,8 @@ int sctp_rcv(struct sk_buff *skb)
 	__skb_pull(skb, skb->h.raw - skb->data);
 	if (skb->len < sizeof(struct sctphdr))
 		goto discard_it;
-	if (sctp_rcv_checksum(skb) < 0)
+	if ((skb->ip_summed != CHECKSUM_UNNECESSARY) &&
+	    (sctp_rcv_checksum(skb) < 0))
 		goto discard_it;
 
 	skb_pull(skb, sizeof(struct sctphdr));

net/sctp/output.c

@@ -295,14 +295,14 @@ int sctp_packet_transmit(struct sctp_packet *packet)
 	struct sctp_transport *tp = packet->transport;
 	struct sctp_association *asoc = tp->asoc;
 	struct sctphdr *sh;
-	__u32 crc32;
+	__u32 crc32 = 0;
 	struct sk_buff *nskb;
 	struct sctp_chunk *chunk, *tmp;
 	struct sock *sk;
 	int err = 0;
 	int padding;		/* How much padding do we need?  */
 	__u8 has_data = 0;
-	struct dst_entry *dst;
+	struct dst_entry *dst = tp->dst;
 
 	SCTP_DEBUG_PRINTK("%s: packet:%p\n", __FUNCTION__, packet);
 
@@ -327,6 +327,19 @@ int sctp_packet_transmit(struct sctp_packet *packet)
 	 */
 	skb_set_owner_w(nskb, sk);
 
+	/* The 'obsolete' field of dst is set to 2 when a dst is freed. */
+	if (!dst || (dst->obsolete > 1)) {
+		dst_release(dst);
+		sctp_transport_route(tp, NULL, sctp_sk(sk));
+		if (asoc && (asoc->param_flags & SPP_PMTUD_ENABLE)) {
+			sctp_assoc_sync_pmtu(asoc);
+		}
+	}
+	nskb->dst = dst_clone(tp->dst);
+	if (!nskb->dst)
+		goto no_route;
+	dst = nskb->dst;
+
 	/* Build the SCTP header.  */
 	sh = (struct sctphdr *)skb_push(nskb, sizeof(struct sctphdr));
 	sh->source = htons(packet->source_port);
@@ -350,6 +363,7 @@ int sctp_packet_transmit(struct sctp_packet *packet)
 	 * Note: Adler-32 is no longer applicable, as has been replaced
 	 * by CRC32-C as described in <draft-ietf-tsvwg-sctpcsum-02.txt>.
 	 */
+	if (!(dst->dev->features & NETIF_F_NO_CSUM))
 		crc32 = sctp_start_cksum((__u8 *)sh, sizeof(struct sctphdr));
 
 	/**
@@ -402,7 +416,12 @@ int sctp_packet_transmit(struct sctp_packet *packet)
 		if (padding)
 			memset(skb_put(chunk->skb, padding), 0, padding);
 
-		crc32 = sctp_update_copy_cksum(skb_put(nskb, chunk->skb->len),
+		if (dst->dev->features & NETIF_F_NO_CSUM)
+			memcpy(skb_put(nskb, chunk->skb->len),
+			       chunk->skb->data, chunk->skb->len);
+		else
+			crc32 = sctp_update_copy_cksum(skb_put(nskb,
+							chunk->skb->len),
 						chunk->skb->data,
 						chunk->skb->len, crc32);
 
@@ -427,6 +446,7 @@ int sctp_packet_transmit(struct sctp_packet *packet)
 	}
 
 	/* Perform final transformation on checksum. */
+	if (!(dst->dev->features & NETIF_F_NO_CSUM))
 		crc32 = sctp_end_cksum(crc32);
 
 	/* 3) Put the resultant value into the checksum field in the
@@ -477,20 +497,6 @@ int sctp_packet_transmit(struct sctp_packet *packet)
 		}
 	}
 
-	dst = tp->dst;
-	/* The 'obsolete' field of dst is set to 2 when a dst is freed. */
-	if (!dst || (dst->obsolete > 1)) {
-		dst_release(dst);
-		sctp_transport_route(tp, NULL, sctp_sk(sk));
-		if (asoc->param_flags & SPP_PMTUD_ENABLE) {
-			sctp_assoc_sync_pmtu(asoc);
-		}
-	}
-
-	nskb->dst = dst_clone(tp->dst);
-	if (!nskb->dst)
-		goto no_route;
-
 	SCTP_DEBUG_PRINTK("***sctp_transmit_packet*** skb len %d\n",
 			  nskb->len);