Subject: Re: [PATCHv2] Refactor update of IPv6 flow destination address for srcrt (RH) option

From: [email-masked] (Arnaud Ebalard)
Date: Tue, 01 Jun 2010 21:17:33 +0200

Hi,

I received a comment (privately) about the fact that the transform isn't
equivalent as its sets final_p in all cases now, and asked if it matters?

It does not: in current code, final_p is always initialized to NULL when
it is declared. I also verified it is not used by anything between the
declaration and the code I replace by the helper.

In fact, one additional thing which can be done is to remove the
initialization final_p to NULL when it is declared. The updated version
below does that.

Patch is against net-2.6. Tested on 2.6.34.

Cheers,

a+

>>From 50e59bf48323777a05476e0d094f15b67194f0bd Mon Sep 17 00:00:00 2001
From: Arnaud Ebalard <[email-masked]>
Date: Tue, 1 Jun 2010 19:40:54 +0200
Subject: [PATCHv2] Refactor update of IPv6 flow destination address for srcrt (RH) option

There are more than a dozen occurrences of following code in the
IPv6 stack:

    if (opt && opt->srcrt) {
            struct rt0_hdr *rt0 = (struct rt0_hdr *) opt->srcrt;
            ipv6_addr_copy(&final, &fl.fl6_dst);
            ipv6_addr_copy(&fl.fl6_dst, rt0->addr);
            final_p = &final;
    }

Replace those with a helper. Note that the helper overrides final_p
in all cases. This is ok as final_p was previously initialized to
NULL when declared.

Signed-off-by: Arnaud Ebalard <[email-masked]>
---
 include/net/ipv6.h               |   13 +++++++++++++
 net/dccp/ipv6.c                  |   30 ++++++------------------------
 net/ipv6/af_inet6.c              |    9 ++-------
 net/ipv6/datagram.c              |   18 ++++--------------
 net/ipv6/inet6_connection_sock.c |    9 ++-------
 net/ipv6/raw.c                   |   10 ++--------
 net/ipv6/syncookies.c            |    9 ++-------
 net/ipv6/tcp_ipv6.c              |   27 ++++++---------------------
 net/ipv6/udp.c                   |   11 +++--------
 9 files changed, 40 insertions(+), 96 deletions(-)

diff --git a/include/net/ipv6.h b/include/net/ipv6.h
index 2600b69..9edfa1c 100644
--- a/include/net/ipv6.h
+++ b/include/net/ipv6.h
@@ -290,6 +290,19 @@ static inline void ipv6_addr_copy(struct in6_addr *a1, const struct in6_addr *a2
 	memcpy(a1, a2, sizeof(struct in6_addr));
 }
 
+static inline struct in6_addr *srcrt_dst_flow_update(struct in6_addr *final,
+						     struct in6_addr *fl6dst,
+						     const struct ipv6_txoptions *opt)
+{
+	if (opt && opt->srcrt) {
+		const struct rt0_hdr *rt0 = (struct rt0_hdr *)opt->srcrt;
+		ipv6_addr_copy(final, fl6dst);
+		ipv6_addr_copy(fl6dst, rt0->addr);
+		return final;
+	}
+	return NULL;
+}
+
 static inline void ipv6_addr_prefix(struct in6_addr *pfx, 
 				    const struct in6_addr *addr,
 				    int plen)
diff --git a/net/dccp/ipv6.c b/net/dccp/ipv6.c
index 0916988..38151db 100644
--- a/net/dccp/ipv6.c
+++ b/net/dccp/ipv6.c
@@ -248,7 +248,7 @@ static int dccp_v6_send_response(struct sock *sk, struct request_sock *req,
 	struct ipv6_pinfo *np = inet6_sk(sk);
 	struct sk_buff *skb;
 	struct ipv6_txoptions *opt = NULL;
-	struct in6_addr *final_p = NULL, final;
+	struct in6_addr *final_p, final;
 	struct flowi fl;
 	int err = -1;
 	struct dst_entry *dst;
@@ -265,13 +265,7 @@ static int dccp_v6_send_response(struct sock *sk, struct request_sock *req,
 
 	opt = np->opt;
 
-	if (opt != NULL && opt->srcrt != NULL) {
-		const struct rt0_hdr *rt0 = (struct rt0_hdr *)opt->srcrt;
-
-		ipv6_addr_copy(&final, &fl.fl6_dst);
-		ipv6_addr_copy(&fl.fl6_dst, rt0->addr);
-		final_p = &final;
-	}
+	final_p = srcrt_dst_flow_update(&final, &fl.fl6_dst, opt);
 
 	err = ip6_dst_lookup(sk, &dst, &fl);
 	if (err)
@@ -545,19 +539,13 @@ static struct sock *dccp_v6_request_recv_sock(struct sock *sk,
 		goto out_overflow;
 
 	if (dst == NULL) {
-		struct in6_addr *final_p = NULL, final;
+		struct in6_addr *final_p, final;
 		struct flowi fl;
 
 		memset(&fl, 0, sizeof(fl));
 		fl.proto = IPPROTO_DCCP;
 		ipv6_addr_copy(&fl.fl6_dst, &ireq6->rmt_addr);
-		if (opt != NULL && opt->srcrt != NULL) {
-			const struct rt0_hdr *rt0 = (struct rt0_hdr *)opt->srcrt;
-
-			ipv6_addr_copy(&final, &fl.fl6_dst);
-			ipv6_addr_copy(&fl.fl6_dst, rt0->addr);
-			final_p = &final;
-		}
+		final_p = srcrt_dst_flow_update(&final, &fl.fl6_dst, opt);
 		ipv6_addr_copy(&fl.fl6_src, &ireq6->loc_addr);
 		fl.oif = sk->sk_bound_dev_if;
 		fl.fl_ip_dport = inet_rsk(req)->rmt_port;
@@ -885,7 +873,7 @@ static int dccp_v6_connect(struct sock *sk, struct sockaddr *uaddr,
 	struct inet_sock *inet = inet_sk(sk);
 	struct ipv6_pinfo *np = inet6_sk(sk);
 	struct dccp_sock *dp = dccp_sk(sk);
-	struct in6_addr *saddr = NULL, *final_p = NULL, final;
+	struct in6_addr *saddr = NULL, *final_p, final;
 	struct flowi fl;
 	struct dst_entry *dst;
 	int addr_type;
@@ -988,13 +976,7 @@ static int dccp_v6_connect(struct sock *sk, struct sockaddr *uaddr,
 	fl.fl_ip_sport = inet->inet_sport;
 	security_sk_classify_flow(sk, &fl);
 
-	if (np->opt != NULL && np->opt->srcrt != NULL) {
-		const struct rt0_hdr *rt0 = (struct rt0_hdr *)np->opt->srcrt;
-
-		ipv6_addr_copy(&final, &fl.fl6_dst);
-		ipv6_addr_copy(&fl.fl6_dst, rt0->addr);
-		final_p = &final;
-	}
+	final_p = srcrt_dst_flow_update(&final, &fl.fl6_dst, np->opt);
 
 	err = ip6_dst_lookup(sk, &dst, &fl);
 	if (err)
diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
index e733942..9df2373 100644
--- a/net/ipv6/af_inet6.c
+++ b/net/ipv6/af_inet6.c
@@ -651,7 +651,7 @@ int inet6_sk_rebuild_header(struct sock *sk)
 
 	if (dst == NULL) {
 		struct inet_sock *inet = inet_sk(sk);
-		struct in6_addr *final_p = NULL, final;
+		struct in6_addr *final_p, final;
 		struct flowi fl;
 
 		memset(&fl, 0, sizeof(fl));
@@ -665,12 +665,7 @@ int inet6_sk_rebuild_header(struct sock *sk)
 		fl.fl_ip_sport = inet->inet_sport;
 		security_sk_classify_flow(sk, &fl);
 
-		if (np->opt && np->opt->srcrt) {
-			struct rt0_hdr *rt0 = (struct rt0_hdr *) np->opt->srcrt;
-			ipv6_addr_copy(&final, &fl.fl6_dst);
-			ipv6_addr_copy(&fl.fl6_dst, rt0->addr);
-			final_p = &final;
-		}
+		final_p = srcrt_dst_flow_update(&final, &fl.fl6_dst, np->opt);
 
 		err = ip6_dst_lookup(sk, &dst, &fl);
 		if (err) {
diff --git a/net/ipv6/datagram.c b/net/ipv6/datagram.c
index 7126846..378fd58 100644
--- a/net/ipv6/datagram.c
+++ b/net/ipv6/datagram.c
@@ -38,10 +38,11 @@ int ip6_datagram_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
 	struct sockaddr_in6	*usin = (struct sockaddr_in6 *) uaddr;
 	struct inet_sock      	*inet = inet_sk(sk);
 	struct ipv6_pinfo      	*np = inet6_sk(sk);
-	struct in6_addr		*daddr, *final_p = NULL, final;
+	struct in6_addr		*daddr, *final_p, final;
 	struct dst_entry	*dst;
 	struct flowi		fl;
 	struct ip6_flowlabel	*flowlabel = NULL;
+	struct ipv6_txoptions   *opt;
 	int			addr_type;
 	int			err;
 
@@ -155,19 +156,8 @@ ipv4_connected:
 
 	security_sk_classify_flow(sk, &fl);
 
-	if (flowlabel) {
-		if (flowlabel->opt && flowlabel->opt->srcrt) {
-			struct rt0_hdr *rt0 = (struct rt0_hdr *) flowlabel->opt->srcrt;
-			ipv6_addr_copy(&final, &fl.fl6_dst);
-			ipv6_addr_copy(&fl.fl6_dst, rt0->addr);
-			final_p = &final;
-		}
-	} else if (np->opt && np->opt->srcrt) {
-		struct rt0_hdr *rt0 = (struct rt0_hdr *)np->opt->srcrt;
-		ipv6_addr_copy(&final, &fl.fl6_dst);
-		ipv6_addr_copy(&fl.fl6_dst, rt0->addr);
-		final_p = &final;
-	}
+	opt = flowlabel ? flowlabel->opt : np->opt;
+	final_p = srcrt_dst_flow_update(&final, &fl.fl6_dst, opt);
 
 	err = ip6_dst_lookup(sk, &dst, &fl);
 	if (err)
diff --git a/net/ipv6/inet6_connection_sock.c b/net/ipv6/inet6_connection_sock.c
index 0c5e3c3..14b5ec5 100644
--- a/net/ipv6/inet6_connection_sock.c
+++ b/net/ipv6/inet6_connection_sock.c
@@ -185,7 +185,7 @@ int inet6_csk_xmit(struct sk_buff *skb)
 	struct ipv6_pinfo *np = inet6_sk(sk);
 	struct flowi fl;
 	struct dst_entry *dst;
-	struct in6_addr *final_p = NULL, final;
+	struct in6_addr *final_p, final;
 
 	memset(&fl, 0, sizeof(fl));
 	fl.proto = sk->sk_protocol;
@@ -199,12 +199,7 @@ int inet6_csk_xmit(struct sk_buff *skb)
 	fl.fl_ip_dport = inet->inet_dport;
 	security_sk_classify_flow(sk, &fl);
 
-	if (np->opt && np->opt->srcrt) {
-		struct rt0_hdr *rt0 = (struct rt0_hdr *)np->opt->srcrt;
-		ipv6_addr_copy(&final, &fl.fl6_dst);
-		ipv6_addr_copy(&fl.fl6_dst, rt0->addr);
-		final_p = &final;
-	}
+	final_p = srcrt_dst_flow_update(&final, &fl.fl6_dst, np->opt);
 
 	dst = __inet6_csk_dst_check(sk, np->dst_cookie);
 
diff --git a/net/ipv6/raw.c b/net/ipv6/raw.c
index 4a4dcbe..f161a54 100644
--- a/net/ipv6/raw.c
+++ b/net/ipv6/raw.c
@@ -725,7 +725,7 @@ static int rawv6_sendmsg(struct kiocb *iocb, struct sock *sk,
 {
 	struct ipv6_txoptions opt_space;
 	struct sockaddr_in6 * sin6 = (struct sockaddr_in6 *) msg->msg_name;
-	struct in6_addr *daddr, *final_p = NULL, final;
+	struct in6_addr *daddr, *final_p, final;
 	struct inet_sock *inet = inet_sk(sk);
 	struct ipv6_pinfo *np = inet6_sk(sk);
 	struct raw6_sock *rp = raw6_sk(sk);
@@ -847,13 +847,7 @@ static int rawv6_sendmsg(struct kiocb *iocb, struct sock *sk,
 	if (ipv6_addr_any(&fl.fl6_src) && !ipv6_addr_any(&np->saddr))
 		ipv6_addr_copy(&fl.fl6_src, &np->saddr);
 
-	/* merge ip6_build_xmit from ip6_output */
-	if (opt && opt->srcrt) {
-		struct rt0_hdr *rt0 = (struct rt0_hdr *) opt->srcrt;
-		ipv6_addr_copy(&final, &fl.fl6_dst);
-		ipv6_addr_copy(&fl.fl6_dst, rt0->addr);
-		final_p = &final;
-	}
+	final_p = srcrt_dst_flow_update(&final, &fl.fl6_dst, opt);
 
 	if (!fl.oif && ipv6_addr_is_multicast(&fl.fl6_dst))
 		fl.oif = np->mcast_oif;
diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c
index 34d1f06..edcaa92 100644
--- a/net/ipv6/syncookies.c
+++ b/net/ipv6/syncookies.c
@@ -240,17 +240,12 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
 	 * me if there is a preferred way.
 	 */
 	{
-		struct in6_addr *final_p = NULL, final;
+		struct in6_addr *final_p, final;
 		struct flowi fl;
 		memset(&fl, 0, sizeof(fl));
 		fl.proto = IPPROTO_TCP;
 		ipv6_addr_copy(&fl.fl6_dst, &ireq6->rmt_addr);
-		if (np->opt && np->opt->srcrt) {
-			struct rt0_hdr *rt0 = (struct rt0_hdr *) np->opt->srcrt;
-			ipv6_addr_copy(&final, &fl.fl6_dst);
-			ipv6_addr_copy(&fl.fl6_dst, rt0->addr);
-			final_p = &final;
-		}
+		final_p = srcrt_dst_flow_update(&final, &fl.fl6_dst, np->opt);
 		ipv6_addr_copy(&fl.fl6_src, &ireq6->loc_addr);
 		fl.oif = sk->sk_bound_dev_if;
 		fl.mark = sk->sk_mark;
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 2b7c3a1..212315a 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -129,7 +129,7 @@ static int tcp_v6_connect(struct sock *sk, struct sockaddr *uaddr,
 	struct inet_connection_sock *icsk = inet_csk(sk);
 	struct ipv6_pinfo *np = inet6_sk(sk);
 	struct tcp_sock *tp = tcp_sk(sk);
-	struct in6_addr *saddr = NULL, *final_p = NULL, final;
+	struct in6_addr *saddr = NULL, *final_p, final;
 	struct flowi fl;
 	struct dst_entry *dst;
 	int addr_type;
@@ -250,12 +250,7 @@ static int tcp_v6_connect(struct sock *sk, struct sockaddr *uaddr,
 	fl.fl_ip_dport = usin->sin6_port;
 	fl.fl_ip_sport = inet->inet_sport;
 
-	if (np->opt && np->opt->srcrt) {
-		struct rt0_hdr *rt0 = (struct rt0_hdr *)np->opt->srcrt;
-		ipv6_addr_copy(&final, &fl.fl6_dst);
-		ipv6_addr_copy(&fl.fl6_dst, rt0->addr);
-		final_p = &final;
-	}
+	final_p = srcrt_dst_flow_update(&final, &fl.fl6_dst, np->opt);
 
 	security_sk_classify_flow(sk, &fl);
 
@@ -477,7 +472,7 @@ static int tcp_v6_send_synack(struct sock *sk, struct request_sock *req,
 	struct ipv6_pinfo *np = inet6_sk(sk);
 	struct sk_buff * skb;
 	struct ipv6_txoptions *opt = NULL;
-	struct in6_addr * final_p = NULL, final;
+	struct in6_addr * final_p, final;
 	struct flowi fl;
 	struct dst_entry *dst;
 	int err = -1;
@@ -494,12 +489,7 @@ static int tcp_v6_send_synack(struct sock *sk, struct request_sock *req,
 	security_req_classify_flow(req, &fl);
 
 	opt = np->opt;
-	if (opt && opt->srcrt) {
-		struct rt0_hdr *rt0 = (struct rt0_hdr *) opt->srcrt;
-		ipv6_addr_copy(&final, &fl.fl6_dst);
-		ipv6_addr_copy(&fl.fl6_dst, rt0->addr);
-		final_p = &final;
-	}
+	final_p = srcrt_dst_flow_update(&final, &fl.fl6_dst, opt);
 
 	err = ip6_dst_lookup(sk, &dst, &fl);
 	if (err)
@@ -1392,18 +1382,13 @@ static struct sock * tcp_v6_syn_recv_sock(struct sock *sk, struct sk_buff *skb,
 		goto out_overflow;
 
 	if (dst == NULL) {
-		struct in6_addr *final_p = NULL, final;
+		struct in6_addr *final_p, final;
 		struct flowi fl;
 
 		memset(&fl, 0, sizeof(fl));
 		fl.proto = IPPROTO_TCP;
 		ipv6_addr_copy(&fl.fl6_dst, &treq->rmt_addr);
-		if (opt && opt->srcrt) {
-			struct rt0_hdr *rt0 = (struct rt0_hdr *) opt->srcrt;
-			ipv6_addr_copy(&final, &fl.fl6_dst);
-			ipv6_addr_copy(&fl.fl6_dst, rt0->addr);
-			final_p = &final;
-		}
+		final_p = srcrt_dst_flow_update(&final, &fl.fl6_dst, opt);
 		ipv6_addr_copy(&fl.fl6_src, &treq->loc_addr);
 		fl.oif = sk->sk_bound_dev_if;
 		fl.mark = sk->sk_mark;
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 87be586..33aa47c 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -927,7 +927,7 @@ int udpv6_sendmsg(struct kiocb *iocb, struct sock *sk,
 	struct inet_sock *inet = inet_sk(sk);
 	struct ipv6_pinfo *np = inet6_sk(sk);
 	struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *) msg->msg_name;
-	struct in6_addr *daddr, *final_p = NULL, final;
+	struct in6_addr *daddr, *final_p, final;
 	struct ipv6_txoptions *opt = NULL;
 	struct ip6_flowlabel *flowlabel = NULL;
 	struct flowi fl;
@@ -1097,14 +1097,9 @@ do_udp_sendmsg:
 		ipv6_addr_copy(&fl.fl6_src, &np->saddr);
 	fl.fl_ip_sport = inet->inet_sport;
 
-	/* merge ip6_build_xmit from ip6_output */
-	if (opt && opt->srcrt) {
-		struct rt0_hdr *rt0 = (struct rt0_hdr *) opt->srcrt;
-		ipv6_addr_copy(&final, &fl.fl6_dst);
-		ipv6_addr_copy(&fl.fl6_dst, rt0->addr);
-		final_p = &final;
+	final_p = srcrt_dst_flow_update(&final, &fl.fl6_dst, opt);
+	if (final_p)
 		connected = 0;
-	}
 
 	if (!fl.oif && ipv6_addr_is_multicast(&fl.fl6_dst)) {
 		fl.oif = np->mcast_oif;
-- 
1.7.1