MFp4 bz_ipv6_fast:

  Add code to handle pre-checked TCP checksums as indicated by mbuf
  flags to save the entire computation for validation if not needed.

  In the IPv6 TCP output path only compute the pseudo-header checksum,
  set the checksum offset in the mbuf field along the appropriate flag
  as done in IPv4.

  In tcp_respond() just initialize the IPv6 payload length to 0 as
  ip6_output() will properly set it.

  Sponsored by:	The FreeBSD Foundation
  Sponsored by:	iXsystems

Reviewed by:	gnn (as part of the whole)
MFC After:	3 days

1 files changed, 20 insertions, 2 deletions

diff --git a/sys/netinet/tcp_input.c b/sys/netinet/tcp_input.c
index 701fafb..5a94c6e 100644
--- a/sys/netinet/tcp_input.c
+++ b/sys/netinet/tcp_input.c
@@ -577,13 +577,31 @@ tcp_input(struct mbuf *m, int off0)
 #ifdef INET6
 	if (isipv6) {
 		/* IP6_EXTHDR_CHECK() is already done at tcp6_input(). */
+
+		if (m->m_len < (sizeof(*ip6) + sizeof(*th))) {
+			m = m_pullup(m, sizeof(*ip6) + sizeof(*th));
+			if (m == NULL) {
+				TCPSTAT_INC(tcps_rcvshort);
+				return;
+			}
+		}
+
 		ip6 = mtod(m, struct ip6_hdr *);
+		th = (struct tcphdr *)((caddr_t)ip6 + off0);
 		tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0;
-		if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) {
+		if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) {
+			if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
+				th->th_sum = m->m_pkthdr.csum_data;
+			else
+				th->th_sum = in6_cksum_pseudo(ip6, tlen,
+				    IPPROTO_TCP, m->m_pkthdr.csum_data);
+			th->th_sum ^= 0xffff;
+		} else
+			th->th_sum = in6_cksum(m, IPPROTO_TCP, off0, tlen);
+		if (th->th_sum) {
 			TCPSTAT_INC(tcps_rcvbadsum);
 			goto drop;
 		}
-		th = (struct tcphdr *)((caddr_t)ip6 + off0);
 
 		/*
 		 * Be proactive about unspecified IPv6 address in source.