[IPV6]: Fix sending extension headers before and including routing header.

Based on suggestion from Masahide Nakamura <nakam@linux-ipv6.org>.
Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>

include/net/ipv6.h

@@ -237,6 +237,8 @@ extern struct ipv6_txoptions *	ipv6_renew_options(struct sock *sk, struct ipv6_t
 						   int newtype,
 						   struct ipv6_opt_hdr __user *newopt,
 						   int newoptlen);
+struct ipv6_txoptions *ipv6_fixup_options(struct ipv6_txoptions *opt_space,
+					  struct ipv6_txoptions *opt);
 
 extern int ip6_frag_nqueues;
 extern atomic_t ip6_frag_mem;

net/ipv6/exthdrs.c

@@ -673,3 +673,22 @@ ipv6_renew_options(struct sock *sk, struct ipv6_txoptions *opt,
 	return ERR_PTR(err);
 }
 
+struct ipv6_txoptions *ipv6_fixup_options(struct ipv6_txoptions *opt_space,
+					  struct ipv6_txoptions *opt)
+{
+	/*
+	 * ignore the dest before srcrt unless srcrt is being included.
+	 * --yoshfuji
+	 */
+	if (opt && opt->dst0opt && !opt->srcrt) {
+		if (opt_space != opt) {
+			memcpy(opt_space, opt, sizeof(*opt_space));
+			opt = opt_space;
+		}
+		opt->opt_nflen -= ipv6_optlen(opt->dst0opt);
+		opt->dst0opt = NULL;
+	}
+
+	return opt;
+}
+

net/ipv6/ip6_flowlabel.c

@@ -225,20 +225,16 @@ struct ipv6_txoptions *fl6_merge_options(struct ipv6_txoptions * opt_space,
 					 struct ip6_flowlabel * fl,
 					 struct ipv6_txoptions * fopt)
 {
-	struct ipv6_txoptions * fl_opt = fl ? fl->opt : NULL;
-
-	if (fopt == NULL || fopt->opt_flen == 0) {
-		if (!fl_opt || !fl_opt->dst0opt || fl_opt->srcrt)
-			return fl_opt;
-	}
-
+	struct ipv6_txoptions * fl_opt = fl->opt;
+	
+	if (fopt == NULL || fopt->opt_flen == 0)
+		return fl_opt;
+	
 	if (fl_opt != NULL) {
 		opt_space->hopopt = fl_opt->hopopt;
-		opt_space->dst0opt = fl_opt->srcrt ? fl_opt->dst0opt : NULL;
+		opt_space->dst0opt = fl_opt->dst0opt;
 		opt_space->srcrt = fl_opt->srcrt;
 		opt_space->opt_nflen = fl_opt->opt_nflen;
-		if (fl_opt->dst0opt && !fl_opt->srcrt)
-			opt_space->opt_nflen -= ipv6_optlen(fl_opt->dst0opt);
 	} else {
 		if (fopt->opt_nflen == 0)
 			return fopt;

net/ipv6/raw.c

@@ -756,7 +756,9 @@ static int rawv6_sendmsg(struct kiocb *iocb, struct sock *sk,
 	}
 	if (opt == NULL)
 		opt = np->opt;
-	opt = fl6_merge_options(&opt_space, flowlabel, opt);
+	if (flowlabel)
+		opt = fl6_merge_options(&opt_space, flowlabel, opt);
+	opt = ipv6_fixup_options(&opt_space, opt);
 
 	fl.proto = proto;
 	rawv6_probe_proto_opt(&fl, msg);

net/ipv6/udp.c

@@ -778,7 +778,9 @@ static int udpv6_sendmsg(struct kiocb *iocb, struct sock *sk,
 	}
 	if (opt == NULL)
 		opt = np->opt;
-	opt = fl6_merge_options(&opt_space, flowlabel, opt);
+	if (flowlabel)
+		opt = fl6_merge_options(&opt_space, flowlabel, opt);
+	opt = ipv6_fixup_options(&opt_space, opt);
 
 	fl->proto = IPPROTO_UDP;
 	ipv6_addr_copy(&fl->fl6_dst, daddr);