net: use skb->csum_not_inet to identify packets needing crc32c

skb->csum_not_inet carries the indication on which algorithm is needed to
compute checksum on skb in the transmit path, when skb->ip_summed is equal
to CHECKSUM_PARTIAL. If skb carries a SCTP packet and crc32c hasn't been
yet written in L4 header, skb->csum_not_inet is assigned to 1; otherwise,
assume Internet Checksum is needed and thus set skb->csum_not_inet to 0.

Suggested-by: Tom Herbert <tom@herbertland.com>
Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Acked-by: Tom Herbert <tom@herbertland.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index c38f890..a43d208 100644 (file)
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -189,12 +189,13 @@
  *
  *   NETIF_F_SCTP_CRC - This feature indicates that a device is capable of
  *     offloading the SCTP CRC in a packet. To perform this offload the stack
- *     will set ip_summed to CHECKSUM_PARTIAL and set csum_start and csum_offset
- *     accordingly. Note the there is no indication in the skbuff that the
- *     CHECKSUM_PARTIAL refers to an SCTP checksum, a driver that supports
- *     both IP checksum offload and SCTP CRC offload must verify which offload
- *     is configured for a packet presumably by inspecting packet headers; in
- *     case, skb_crc32c_csum_help is provided to compute CRC on SCTP packets.
+ *     will set set csum_start and csum_offset accordingly, set ip_summed to
+ *     CHECKSUM_PARTIAL and set csum_not_inet to 1, to provide an indication in
+ *     the skbuff that the CHECKSUM_PARTIAL refers to CRC32c.
+ *     A driver that supports both IP checksum offload and SCTP CRC32c offload
+ *     must verify which offload is configured for a packet by testing the
+ *     value of skb->csum_not_inet; skb_crc32c_csum_help is provided to resolve
+ *     CHECKSUM_PARTIAL on skbs where csum_not_inet is set to 1.
  *
  *   NETIF_F_FCOE_CRC - This feature indicates that a device is capable of
  *     offloading the FCOE CRC in a packet. To perform this offload the stack
@@ -557,6 +558,7 @@ typedef unsigned char *sk_buff_data_t;
  *     @wifi_acked_valid: wifi_acked was set
  *     @wifi_acked: whether frame was acked on wifi or not
  *     @no_fcs:  Request NIC to treat last 4 bytes as Ethernet FCS
+ *     @csum_not_inet: use CRC32c to resolve CHECKSUM_PARTIAL
  *     @dst_pending_confirm: need to confirm neighbour
   *    @napi_id: id of the NAPI struct this skb came from
  *     @secmark: security marking
@@ -685,7 +687,7 @@ struct sk_buff {
        __u8                    csum_valid:1;
        __u8                    csum_complete_sw:1;
        __u8                    csum_level:2;
-       __u8                    __csum_bad_unused:1; /* one bit hole */
+       __u8                    csum_not_inet:1;
 
        __u8                    dst_pending_confirm:1;
 #ifdef CONFIG_IPV6_NDISC_NODETYPE

diff --git a/net/core/dev.c b/net/core/dev.c
index f0281ff..71107d1 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2649,6 +2649,7 @@ int skb_crc32c_csum_help(struct sk_buff *skb)
                                                  crc32c_csum_stub));
        *(__le32 *)(skb->data + offset) = crc32c_csum;
        skb->ip_summed = CHECKSUM_NONE;
+       skb->csum_not_inet = 0;
 out:
        return ret;
 }

diff --git a/net/sched/act_csum.c b/net/sched/act_csum.c
index ab6fdbd..3317a2f 100644 (file)
--- a/net/sched/act_csum.c
+++ b/net/sched/act_csum.c
@@ -350,6 +350,7 @@ static int tcf_csum_sctp(struct sk_buff *skb, unsigned int ihl,
        sctph->checksum = sctp_compute_cksum(skb,
                                             skb_network_offset(skb) + ihl);
        skb->ip_summed = CHECKSUM_NONE;
+       skb->csum_not_inet = 0;
 
        return 1;
 }

diff --git a/net/sctp/offload.c b/net/sctp/offload.c
index b671984..275925b 100644 (file)
--- a/net/sctp/offload.c
+++ b/net/sctp/offload.c
@@ -35,6 +35,7 @@
 static __le32 sctp_gso_make_checksum(struct sk_buff *skb)
 {
        skb->ip_summed = CHECKSUM_NONE;
+       skb->csum_not_inet = 0;
        return sctp_compute_cksum(skb, skb_transport_offset(skb));
 }
 

diff --git a/net/sctp/output.c b/net/sctp/output.c
index 1409a87..e2edf2e 100644 (file)
--- a/net/sctp/output.c
+++ b/net/sctp/output.c
@@ -538,6 +538,7 @@ merge:
        } else {
 chksum:
                head->ip_summed = CHECKSUM_PARTIAL;
+               head->csum_not_inet = 1;
                head->csum_start = skb_transport_header(head) - head->head;
                head->csum_offset = offsetof(struct sctphdr, checksum);
        }