Perform MSS fixups on incoming packets as well as outgoing.

MFC after: 1 week

1 files changed, 43 insertions, 32 deletions

diff --git a/usr.sbin/ppp/tcpmss.c b/usr.sbin/ppp/tcpmss.c
index f8debc8..50606eb 100644
--- a/usr.sbin/ppp/tcpmss.c
+++ b/usr.sbin/ppp/tcpmss.c
@@ -70,37 +70,6 @@
 #define MAXMSS(mtu) (mtu - sizeof(struct ip) - sizeof(struct tcphdr)) 
 
 
-static void MSSFixup(struct tcphdr *, ssize_t, u_int16_t);
-
-
-static struct mbuf *
-tcpmss_LayerPush(struct bundle *bundle, struct link *l, struct mbuf *bp,
-                 int pri, u_short *proto)
-{
-  struct ip *pip;
-  int hlen, plen;
-
-  if (!Enabled(bundle, OPT_TCPMSSFIXUP))
-    return bp;
-
-  bp = m_pullup(bp);
-  plen = m_length(bp);
-  pip = (struct ip *)MBUF_CTOP(bp);
-  hlen = pip->ip_hl << 2;
-
-  /*
-   * Check for MSS option only for TCP packets with zero fragment offsets
-   * and correct total and header lengths.
-   */
-  if (pip->ip_p == IPPROTO_TCP && (ntohs(pip->ip_off) & IP_OFFMASK) == 0 &&
-      ntohs(pip->ip_len) == plen && hlen <= plen &&
-      plen - hlen >= sizeof(struct tcphdr))
-    MSSFixup((struct tcphdr *)(MBUF_CTOP(bp) + hlen), plen - hlen,
-             MAXMSS(bundle->iface->mtu));
-
-  return bp;
-}
-
 /*-
  * The following macro is used to update an
  * internet checksum.  "acc" is a 32-bit
@@ -168,4 +137,46 @@ MSSFixup(struct tcphdr *tc, ssize_t pktlen, u_int16_t maxmss)
   }
 }
 
-struct layer tcpmsslayer = { LAYER_PROTO, "tcpmss", tcpmss_LayerPush, NULL };
+static struct mbuf *
+tcpmss_Check(struct bundle *bundle, struct mbuf *bp)
+{
+  struct ip *pip;
+  int hlen, plen;
+
+  if (!Enabled(bundle, OPT_TCPMSSFIXUP))
+    return bp;
+
+  bp = m_pullup(bp);
+  plen = m_length(bp);
+  pip = (struct ip *)MBUF_CTOP(bp);
+  hlen = pip->ip_hl << 2;
+
+  /*
+   * Check for MSS option only for TCP packets with zero fragment offsets
+   * and correct total and header lengths.
+   */
+  if (pip->ip_p == IPPROTO_TCP && (ntohs(pip->ip_off) & IP_OFFMASK) == 0 &&
+      ntohs(pip->ip_len) == plen && hlen <= plen &&
+      plen - hlen >= sizeof(struct tcphdr))
+    MSSFixup((struct tcphdr *)(MBUF_CTOP(bp) + hlen), plen - hlen,
+             MAXMSS(bundle->iface->mtu));
+
+  return bp;
+}
+
+static struct mbuf *
+tcpmss_LayerPush(struct bundle *bundle, struct link *l, struct mbuf *bp,
+                 int pri, u_short *proto)
+{
+	return tcpmss_Check(bundle, bp);
+}
+
+static struct mbuf *
+tcpmss_LayerPull(struct bundle *bundle, struct link *l, struct mbuf *bp,
+                 u_short *proto)
+{
+	return tcpmss_Check(bundle, bp);
+}
+
+struct layer tcpmsslayer =
+  { LAYER_PROTO, "tcpmss", tcpmss_LayerPush, tcpmss_LayerPull };