Bug #844 PR# 846: --fixhdrlen option

added to control action on packet length changes Verification ``` ~/git/tcpreplay/build Bug_703_844_PR_846_optionally_fix_pkt_hdr_len* ⇡ ❯ src/tcprewrite --cachefile=pcaps/pcap.cache \ --infile=pcaps/cap-original-packet-3.pcap \ --outfile=pcaps/cap-4.5.0-packet-out.pcap \ --endpoints=10.200.1.1:10.200.1.2 Warning in ../../src/tcprewrite.c:post_args() line 231: pcaps/cap-original-packet-3.pcap was captured using a snaplen of 1514 bytes. This may mean you have truncated packets. ~/git/tcpreplay/build Bug_703_844_PR_846_optionally_fix_pkt_hdr_len* ⇡ ❯ diff pcaps/cap-4.4.0-packet-3.pcap pcaps/cap-4.5.0-packet-out.pcap ~/git/tcpreplay/build Bug_703_844_PR_846_optionally_fix_pkt_hdr_len* ⇡ ❯ ```
appneta · Jun 1, 2024 · 859728b · 859728b
1 parent b4148e7
commit 859728b
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diff --git a/docs/CHANGELOG b/docs/CHANGELOG
@@ -1,4 +1,6 @@
 06/01/2024 Version 4.5.0-beta1
+    - --fixhdrlen option added to control action on packet length changes (#846)
+    - incorrect checksum for certain IPv4 packets - fixed by #846 (#844)
     - add check for IPv6 extension header length (#827 #842)
     - add check for empty CIDR (#824 #843)
     - GitHub template for pull requests (#839)

diff --git a/docs/CREDIT b/docs/CREDIT
@@ -123,7 +123,8 @@ GithHub @plangarbalint
 
 Chuck Cottrill <GitHub @ChuckCottrill>
     - handle IPv6 fragment extensions
-
+    - --fixhdrlen option
+    - bug fixes
 
 Martin 'JaMa' Jansa <GitHub @shr-project>
     - configure.ac: unify search dirs for pcap and add lib32
diff --git a/src/tcpedit/parse_args.c b/src/tcpedit/parse_args.c
@@ -98,8 +98,6 @@ tcpedit_post_args(tcpedit_t *tcpedit)
     /* --fixhdrlen */
     if (HAVE_OPT(FIXHDRLEN))
         tcpedit->fixhdrlen = true;
-    else
-        tcpedit->fixhdrlen = false;
 
     /* --efcs */
     if (HAVE_OPT(EFCS))

diff --git a/src/tcpedit/tcpedit.c b/src/tcpedit/tcpedit.c
@@ -321,8 +321,7 @@ tcpedit_packet(tcpedit_t *tcpedit, struct pcap_pkthdr **pkthdr, u_char **pktdata
         /* ensure IP header length is correct */
         int changed = 0;
         if (ip_hdr != NULL) {
-            fix_ipv4_length(*pkthdr, ip_hdr, l2len);
-            changed = 1;
+            changed = fix_ipv4_length(*pkthdr, ip_hdr, l2len);
         } else if (ip6_hdr != NULL) {
             changed = fix_ipv6_length(*pkthdr, ip6_hdr, l2len);
         }

diff --git a/src/tcpedit/tcpedit_opts.def b/src/tcpedit/tcpedit_opts.def
@@ -172,13 +172,12 @@ EOText;
 
 flag = {
     name        = fixhdrlen;
-    // value       = C;
-    descrip     = "fix IP/TCP header len";
+    descrip     = "Alter IP/TCP header len to match packet length";
     doc         = <<- EOText
 By default, tcpreplay will send packets with the original packet length,
 However, you may want the packet length revised to minimum packet size.
 Using this option, tcpreplay will rewrite (fix) the packet length,
-and recalculate checksums.
+and recalculate checksums when packet length changes.
 Caution: undesired packet changes may occur when this option is specified.
 EOText;
 };