Author: ae
Date: Tue Aug 13 12:47:53 2019
New Revision: 350974
URL: https://svnweb.freebsd.org/changeset/base/350974

Log:
  Save ip_ttl value and restore it after checksum calculation.
  
  Since ipvoly is used for checksum calculation, part of original IP
  header is zeroed. This part includes ip_ttl field, that can be used
  later in IP_MINTTL socket option handling.
  
  PR:           239799
  MFC after:    1 week

Modified:
  head/sys/netinet/tcp_input.c

Modified: head/sys/netinet/tcp_input.c
==============================================================================
--- head/sys/netinet/tcp_input.c        Tue Aug 13 12:41:15 2019        
(r350973)
+++ head/sys/netinet/tcp_input.c        Tue Aug 13 12:47:53 2019        
(r350974)
@@ -554,6 +554,7 @@ tcp_input(struct mbuf **mp, int *offp, int proto)
        int optlen = 0;
 #ifdef INET
        int len;
+       uint8_t ipttl;
 #endif
        int tlen = 0, off;
        int drop_hdrlen;
@@ -676,6 +677,7 @@ tcp_input(struct mbuf **mp, int *offp, int proto)
                         * Checksum extended TCP header and data.
                         */
                        len = off0 + tlen;
+                       ipttl = ip->ip_ttl;
                        bzero(ipov->ih_x1, sizeof(ipov->ih_x1));
                        ipov->ih_len = htons(tlen);
                        th->th_sum = in_cksum(m, len);
@@ -684,6 +686,7 @@ tcp_input(struct mbuf **mp, int *offp, int proto)
                        /* Reset TOS bits */
                        ip->ip_tos = iptos;
                        /* Re-initialization for later version check */
+                       ip->ip_ttl = ipttl;
                        ip->ip_v = IPVERSION;
                        ip->ip_hl = off0 >> 2;
                }
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