net: use skb_is_gso_sctp() instead of open-coding

As well as the basic conversion, I noticed that a lot of the
SCTP code checks gso_type without first checking skb_is_gso()
so I have added that where appropriate.

Also, document the helper.

Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: Daniel Axtens <dja@axtens.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

6 files changed, 12 insertions, 9 deletions

diff --git a/Documentation/networking/segmentation-offloads.txt b/Documentation/networking/segmentation-offloads.txt
index fc0c949e7f9c..aca542ec125c 100644
--- a/Documentation/networking/segmentation-offloads.txt
+++ b/Documentation/networking/segmentation-offloads.txt
@@ -155,7 +155,10 @@ Therefore, any code in the core networking stack must be aware of the
 possibility that gso_size will be GSO_BY_FRAGS and handle that case
 appropriately.
 
-There are a couple of helpers to make this easier:
+There are some helpers to make this easier:
+
+ - skb_is_gso(skb) && skb_is_gso_sctp(skb) is the best way to see if
+   an skb is an SCTP GSO skb.
 
  - For size checks, the skb_gso_validate_*_len family of helpers correctly
    considers GSO_BY_FRAGS.
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 0bb0d8877954..baf990528943 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -4904,7 +4904,7 @@ static unsigned int skb_gso_transport_seglen(const struct sk_buff *skb)
                         thlen += inner_tcp_hdrlen(skb);
         } else if (likely(shinfo->gso_type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6))) {
                 thlen = tcp_hdrlen(skb);
-        } else if (unlikely(shinfo->gso_type & SKB_GSO_SCTP)) {
+        } else if (unlikely(skb_is_gso_sctp(skb))) {
                 thlen = sizeof(struct sctphdr);
         }
         /* UFO sets gso_size to the size of the fragmentation
diff --git a/net/sched/act_csum.c b/net/sched/act_csum.c
index b7ba9b06b147..24b2e8e681cf 100644
--- a/net/sched/act_csum.c
+++ b/net/sched/act_csum.c
@@ -350,7 +350,7 @@ static int tcf_csum_sctp(struct sk_buff *skb, unsigned int ihl,
 {
         struct sctphdr *sctph;
 
-        if (skb_is_gso(skb) && skb_shinfo(skb)->gso_type & SKB_GSO_SCTP)
+        if (skb_is_gso(skb) && skb_is_gso_sctp(skb))
                 return 1;
 
         sctph = tcf_csum_skb_nextlayer(skb, ihl, ipl, sizeof(*sctph));
diff --git a/net/sctp/input.c b/net/sctp/input.c
index 0247cc432e02..b381d78548ac 100644
--- a/net/sctp/input.c
+++ b/net/sctp/input.c
@@ -106,6 +106,7 @@ int sctp_rcv(struct sk_buff *skb)
         int family;
         struct sctp_af *af;
         struct net *net = dev_net(skb->dev);
+        bool is_gso = skb_is_gso(skb) && skb_is_gso_sctp(skb);
 
         if (skb->pkt_type != PACKET_HOST)
                 goto discard_it;
@@ -123,8 +124,7 @@ int sctp_rcv(struct sk_buff *skb)
          * it's better to just linearize it otherwise crc computing
          * takes longer.
          */
-        if ((!(skb_shinfo(skb)->gso_type & SKB_GSO_SCTP) &&
-             skb_linearize(skb)) ||
+        if ((!is_gso && skb_linearize(skb)) ||
             !pskb_may_pull(skb, sizeof(struct sctphdr)))
                 goto discard_it;
 
@@ -135,7 +135,7 @@ int sctp_rcv(struct sk_buff *skb)
         if (skb_csum_unnecessary(skb))
                 __skb_decr_checksum_unnecessary(skb);
         else if (!sctp_checksum_disable &&
-                 !(skb_shinfo(skb)->gso_type & SKB_GSO_SCTP) &&
+                 !is_gso &&
                  sctp_rcv_checksum(net, skb) < 0)
                 goto discard_it;
         skb->csum_valid = 1;
@@ -1218,7 +1218,7 @@ static struct sctp_association *__sctp_rcv_lookup_harder(struct net *net,
          * issue as packets hitting this are mostly INIT or INIT-ACK and
          * those cannot be on GSO-style anyway.
          */
-        if ((skb_shinfo(skb)->gso_type & SKB_GSO_SCTP) == SKB_GSO_SCTP)
+        if (skb_is_gso(skb) && skb_is_gso_sctp(skb))
                 return NULL;
 
         ch = (struct sctp_chunkhdr *)skb->data;
diff --git a/net/sctp/inqueue.c b/net/sctp/inqueue.c
index 48392552ee7c..23ebc5318edc 100644
--- a/net/sctp/inqueue.c
+++ b/net/sctp/inqueue.c
@@ -170,7 +170,7 @@ next_chunk:
 
                 chunk = list_entry(entry, struct sctp_chunk, list);
 
-                if ((skb_shinfo(chunk->skb)->gso_type & SKB_GSO_SCTP) == SKB_GSO_SCTP) {
+                if (skb_is_gso(chunk->skb) && skb_is_gso_sctp(chunk->skb)) {
                         /* GSO-marked skbs but without frags, handle
                          * them normally
                          */
diff --git a/net/sctp/offload.c b/net/sctp/offload.c
index 35bc7106d182..123e9f2dc226 100644
--- a/net/sctp/offload.c
+++ b/net/sctp/offload.c
@@ -45,7 +45,7 @@ static struct sk_buff *sctp_gso_segment(struct sk_buff *skb,
         struct sk_buff *segs = ERR_PTR(-EINVAL);
         struct sctphdr *sh;
 
-        if (!(skb_shinfo(skb)->gso_type & SKB_GSO_SCTP))
+        if (!skb_is_gso_sctp(skb))
                 goto out;
 
         sh = sctp_hdr(skb);