skbuff: introduce skb_gso_validate_mtu

skb_gso_network_seglen is not enough for checking fragment sizes if
skb is using GSO_BY_FRAGS as we have to check frag per frag.

This patch introduces skb_gso_validate_mtu, based on the former, which
will wrap the use case inside it as all calls to skb_gso_network_seglen
were to validate if it fits on a given TMU, and improve the check.

Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Tested-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 329a0a9..aa3f9d7 100644 (file)
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2992,6 +2992,7 @@ void skb_split(struct sk_buff *skb, struct sk_buff *skb1, const u32 len);
 int skb_shift(struct sk_buff *tgt, struct sk_buff *skb, int shiftlen);
 void skb_scrub_packet(struct sk_buff *skb, bool xnet);
 unsigned int skb_gso_transport_seglen(const struct sk_buff *skb);
+bool skb_gso_validate_mtu(const struct sk_buff *skb, unsigned int mtu);
 struct sk_buff *skb_segment(struct sk_buff *skb, netdev_features_t features);
 struct sk_buff *skb_vlan_untag(struct sk_buff *skb);
 int skb_ensure_writable(struct sk_buff *skb, int write_len);

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 97c32c7..5ca562b 100644 (file)
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -4392,6 +4392,37 @@ unsigned int skb_gso_transport_seglen(const struct sk_buff *skb)
 }
 EXPORT_SYMBOL_GPL(skb_gso_transport_seglen);
 
+/**
+ * skb_gso_validate_mtu - Return in case such skb fits a given MTU
+ *
+ * @skb: GSO skb
+ *
+ * skb_gso_validate_mtu validates if a given skb will fit a wanted MTU
+ * once split.
+ */
+bool skb_gso_validate_mtu(const struct sk_buff *skb, unsigned int mtu)
+{
+       const struct skb_shared_info *shinfo = skb_shinfo(skb);
+       const struct sk_buff *iter;
+       unsigned int hlen;
+
+       hlen = skb_gso_network_seglen(skb);
+
+       if (shinfo->gso_size != GSO_BY_FRAGS)
+               return hlen <= mtu;
+
+       /* Undo this so we can re-use header sizes */
+       hlen -= GSO_BY_FRAGS;
+
+       skb_walk_frags(skb, iter) {
+               if (hlen + skb_headlen(iter) > mtu)
+                       return false;
+       }
+
+       return true;
+}
+EXPORT_SYMBOL_GPL(skb_gso_validate_mtu);
+
 static struct sk_buff *skb_reorder_vlan_header(struct sk_buff *skb)
 {
        if (skb_cow(skb, skb_headroom(skb)) < 0) {

diff --git a/net/ipv4/ip_forward.c b/net/ipv4/ip_forward.c
index cbfb180..9f0a7b9 100644 (file)
--- a/net/ipv4/ip_forward.c
+++ b/net/ipv4/ip_forward.c
@@ -54,7 +54,7 @@ static bool ip_exceeds_mtu(const struct sk_buff *skb, unsigned int mtu)
        if (skb->ignore_df)
                return false;
 
-       if (skb_is_gso(skb) && skb_gso_network_seglen(skb) <= mtu)
+       if (skb_is_gso(skb) && skb_gso_validate_mtu(skb, mtu))
                return false;
 
        return true;

diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 124bf0a..cbac493 100644 (file)
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -225,7 +225,7 @@ static int ip_finish_output_gso(struct net *net, struct sock *sk,
 
        /* common case: locally created skb or seglen is <= mtu */
        if (((IPCB(skb)->flags & IPSKB_FORWARDED) == 0) ||
-             skb_gso_network_seglen(skb) <= mtu)
+             skb_gso_validate_mtu(skb, mtu))
                return ip_finish_output2(net, sk, skb);
 
        /* Slowpath -  GSO segment length is exceeding the dst MTU.

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index cbf127a..6b2f60a 100644 (file)
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -368,7 +368,7 @@ static bool ip6_pkt_too_big(const struct sk_buff *skb, unsigned int mtu)
        if (skb->ignore_df)
                return false;
 
-       if (skb_is_gso(skb) && skb_gso_network_seglen(skb) <= mtu)
+       if (skb_is_gso(skb) && skb_gso_validate_mtu(skb, mtu))
                return false;
 
        return true;

diff --git a/net/mpls/af_mpls.c b/net/mpls/af_mpls.c
index 0b80a71..7a4aa34 100644 (file)
--- a/net/mpls/af_mpls.c
+++ b/net/mpls/af_mpls.c
@@ -91,7 +91,7 @@ bool mpls_pkt_too_big(const struct sk_buff *skb, unsigned int mtu)
        if (skb->len <= mtu)
                return false;
 
-       if (skb_is_gso(skb) && skb_gso_network_seglen(skb) <= mtu)
+       if (skb_is_gso(skb) && skb_gso_validate_mtu(skb, mtu))
                return false;
 
        return true;