From d109e3131be86dce467aa2d9563c3b25349553ef Mon Sep 17 00:00:00 2001
From: Gerhard Rieger <gerhard@dest-unreach.org>
Date: Sat, 12 Dec 2020 13:47:40 +0100
Subject: [PATCH] Added option ip-transparent (socket option IP_TRANSPARENT)

---
 CHANGES      | 3 +++
 doc/socat.yo | 4 ++++
 filan.c      | 3 +++
 xio-ip.c     | 3 +++
 xio-ip.h     | 1 +
 xioopts.c    | 6 ++++++
 xioopts.h    | 3 +++
 7 files changed, 23 insertions(+)

diff --git a/CHANGES b/CHANGES
index f68d1ab..21cb847 100644
--- a/CHANGES
+++ b/CHANGES
@@ -142,6 +142,9 @@ New features:
 	Added options -r and -R for raw dump of transferred data to files.
 	Test: OPTION_RAW_DUMP
 
+	Added option ip-transparent (socket option IP_TRANSPARENT)
+	Thanks to Wang Shanker for sending a patch.
+
 ####################### V 1.7.3.4:
 
 Corrections:
diff --git a/doc/socat.yo b/doc/socat.yo
index 98698ae..e489dd5 100644
--- a/doc/socat.yo
+++ b/doc/socat.yo
@@ -2116,6 +2116,10 @@ dit(bf(tt(ip-multicast-loop=<bool>)))
 label(OPTION_IP_MULTICAST_TTL)
 dit(bf(tt(ip-multicast-ttl=<byte>)))
    Sets the TTL used for outgoing multicast traffic. Default is 1.
+label(OPTOIN_IP_TRANSPARENT)
+dit(bf(tt(ip-transparent)))
+   Sets the IP_TRANSPARENT socket option.
+   This option might require root privilege.
 label(OPTION_RES_DEBUG)dit(bf(tt(res-debug)))
 label(OPTION_RES_AAONLY)dit(bf(tt(res-aaonly)))
 label(OPTION_RES_USEVC)dit(bf(tt(res-usevc)))
diff --git a/filan.c b/filan.c
index 7d7ceb2..cef23c1 100644
--- a/filan.c
+++ b/filan.c
@@ -745,6 +745,9 @@ int ipan(int fd, FILE *outfile) {
 #ifdef IP_RECVTOS
       {IP_RECVTOS,      "IP_RECVTOS"},
 #endif
+#ifdef IP_TRANSPARENT
+      {IP_TRANSPARENT,  "IP_TRANSPARENT"},
+#endif
 #ifdef IP_MTU
       {IP_MTU,          "IP_MTU"},
 #endif
diff --git a/xio-ip.c b/xio-ip.c
index ad99a64..afa3c94 100644
--- a/xio-ip.c
+++ b/xio-ip.c
@@ -50,6 +50,9 @@ const struct optdesc opt_ip_mtu_discover={"ip-mtu-discover","mtudiscover",OPT_IP
 #ifdef IP_MTU
 const struct optdesc opt_ip_mtu     = { "ip-mtu",     "mtu",       OPT_IP_MTU,     GROUP_SOCK_IP, PH_PASTSOCKET, TYPE_INT, OFUNC_SOCKOPT, SOL_IP, IP_MTU };
 #endif
+#ifdef IP_TRANSPARENT
+const struct optdesc opt_ip_transparent = {"ip-transparent", "transparent", OPT_IP_TRANSPARENT, GROUP_SOCK_IP, PH_PREBIND, TYPE_BOOL, OFUNC_SOCKOPT, SOL_IP, IP_TRANSPARENT};
+#endif
 #ifdef IP_FREEBIND
 const struct optdesc opt_ip_freebind= { "ip-freebind","freebind",  OPT_IP_FREEBIND,GROUP_SOCK_IP, PH_PASTSOCKET, TYPE_INT, OFUNC_SOCKOPT, SOL_IP, IP_FREEBIND };
 #endif
diff --git a/xio-ip.h b/xio-ip.h
index eb744d8..801bd95 100644
--- a/xio-ip.h
+++ b/xio-ip.h
@@ -26,6 +26,7 @@ extern const struct optdesc opt_ip_pktoptions;
 extern const struct optdesc opt_ip_add_membership;
 extern const struct optdesc opt_ip_recvdstaddr;
 extern const struct optdesc opt_ip_recvif;
+extern const struct optdesc opt_ip_transparent;
 
 extern const struct optdesc opt_res_debug;
 extern const struct optdesc opt_res_aaonly;
diff --git a/xioopts.c b/xioopts.c
index d9fe679..9947001 100644
--- a/xioopts.c
+++ b/xioopts.c
@@ -719,6 +719,9 @@ const struct optname optionnames[] = {
 	IF_IP     ("ip-router-alert",	&opt_ip_router_alert)
 #endif
 	IF_IP     ("ip-tos",	&opt_ip_tos)
+#ifdef IP_TRANSPARENT
+	IF_IP     ("ip-transparent",    &opt_ip_transparent)
+#endif
 	IF_IP     ("ip-ttl",	&opt_ip_ttl)
 #ifdef IP_FREEBIND
 	IF_IP     ("ipfreebind",	&opt_ip_freebind)
@@ -1691,6 +1694,9 @@ const struct optname optionnames[] = {
 #endif
 	IF_IP     ("tos",	&opt_ip_tos)
 	IF_TERMIOS("tostop",	&opt_tostop)
+#ifdef IP_TRANSPARENT
+	IF_IP     ("transparent",    &opt_ip_transparent)
+#endif
 	IF_OPEN   ("trunc",	&opt_o_trunc)
 #if HAVE_FTRUNCATE64
 	IF_ANY    ("truncate",	&opt_ftruncate64)
diff --git a/xioopts.h b/xioopts.h
index 08056d8..30e9fd2 100644
--- a/xioopts.h
+++ b/xioopts.h
@@ -423,6 +423,9 @@ enum e_optcode {
    OPT_IP_ROUTER_ALERT,
 #endif
    OPT_IP_TOS,
+#ifdef IP_TRANSPARENT
+   OPT_IP_TRANSPARENT,
+#endif
    OPT_IP_TTL,
    OPT_ISIG,		/* termios.c_lflag */
    OPT_ISPEED,		/* termios.c_ispeed */