Author: tuexen
Date: Thu Sep 19 10:27:47 2019
New Revision: 352512
URL: https://svnweb.freebsd.org/changeset/base/352512

Log:
  When the RACK stack computes the space for user data in a TCP segment,
  it wasn't taking the IP level options into account. This patch fixes this.
  In addition, it also corrects a KASSERT and adds protection code to assure
  that the IP header chain and the TCP head fit in the first fragment as
  required by RFC 7112.
  
  Reviewed by:          rrs@
  MFC after:            3 days
  Sponsored by:         Nertflix, Inc.
  Differential Revision:        https://reviews.freebsd.org/D21666

Modified:
  head/sys/netinet/tcp_stacks/rack.c

Modified: head/sys/netinet/tcp_stacks/rack.c
==============================================================================
--- head/sys/netinet/tcp_stacks/rack.c  Thu Sep 19 10:22:29 2019        
(r352511)
+++ head/sys/netinet/tcp_stacks/rack.c  Thu Sep 19 10:27:47 2019        
(r352512)
@@ -7840,7 +7840,16 @@ send:
                hdrlen += sizeof(struct udphdr);
        }
 #endif
-       ipoptlen = 0;
+#ifdef INET6
+       if (isipv6)
+               ipoptlen = ip6_optlen(tp->t_inpcb);
+       else
+#endif
+       if (tp->t_inpcb->inp_options)
+               ipoptlen = tp->t_inpcb->inp_options->m_len -
+                   offsetof(struct ipoption, ipopt_list);
+       else
+               ipoptlen = 0;
 #if defined(IPSEC) || defined(IPSEC_SUPPORT)
        ipoptlen += ipsec_optlen;
 #endif
@@ -7913,6 +7922,18 @@ send:
                                sendalot = 1;
 
                } else {
+                       if (optlen + ipoptlen > tp->t_maxseg) {
+                               /*
+                                * Since we don't have enough space to put
+                                * the IP header chain and the TCP header in
+                                * one packet as required by RFC 7112, don't
+                                * send it.
+                                */
+                               SOCKBUF_UNLOCK(&so->so_snd);
+                               error = EMSGSIZE;
+                               sack_rxmit = 0;
+                               goto out;
+                       }
                        len = tp->t_maxseg - optlen - ipoptlen;
                        sendalot = 1;
                }
@@ -8414,15 +8435,9 @@ send:
                m->m_pkthdr.csum_flags |= CSUM_TSO;
                m->m_pkthdr.tso_segsz = tp->t_maxseg - optlen;
        }
-#if defined(IPSEC) || defined(IPSEC_SUPPORT)
-       KASSERT(len + hdrlen + ipoptlen - ipsec_optlen == m_length(m, NULL),
-           ("%s: mbuf chain shorter than expected: %d + %u + %u - %u != %u",
-           __func__, len, hdrlen, ipoptlen, ipsec_optlen, m_length(m, NULL)));
-#else
-       KASSERT(len + hdrlen + ipoptlen == m_length(m, NULL),
-           ("%s: mbuf chain shorter than expected: %d + %u + %u != %u",
-           __func__, len, hdrlen, ipoptlen, m_length(m, NULL)));
-#endif
+       KASSERT(len + hdrlen == m_length(m, NULL),
+           ("%s: mbuf chain different than expected: %d + %u != %u",
+           __func__, len, hdrlen, m_length(m, NULL)));
 
 #ifdef TCP_HHOOK
        /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */
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