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Date: 27 Mar 2007 16:18:20 +0200
From: Andi Kleen <andi@...stfloor.org>
To: John Heffner <jheffner@....edu>
Cc: David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
Michael Kerrisk <mtk-manpages@....net>
Subject: Re: [PATCH 3/3] [NET] Add IP(V6)_PMTUDISC_RPOBE
John Heffner <jheffner@....edu> writes:
> Add IP(V6)_PMTUDISC_PROBE value for IP(V6)_MTU_DISCOVER. This option forces
> us not to fragment, but does not make use of the kernel path MTU discovery.
> That is, it allows for user-mode MTU probing (or, packetization-layer path
> MTU discovery). This is particularly useful for diagnostic utilities, like
> traceroute/tracepath.
You should probably send a manpages update to the manpages maintainer too
(cc'ed with fullquote)
-Andi
>
> Signed-off-by: John Heffner <jheffner@....edu>
> ---
> include/linux/in.h | 1 +
> include/linux/in6.h | 1 +
> include/linux/skbuff.h | 3 ++-
> include/net/ip.h | 2 +-
> net/core/skbuff.c | 2 ++
> net/ipv4/ip_output.c | 14 ++++++++++----
> net/ipv4/ip_sockglue.c | 2 +-
> net/ipv4/raw.c | 3 +++
> net/ipv6/ip6_output.c | 12 ++++++++----
> net/ipv6/ipv6_sockglue.c | 2 +-
> net/ipv6/raw.c | 3 +++
> 11 files changed, 33 insertions(+), 12 deletions(-)
>
> diff --git a/include/linux/in.h b/include/linux/in.h
> index 1912e7c..2dc1f8a 100644
> --- a/include/linux/in.h
> +++ b/include/linux/in.h
> @@ -83,6 +83,7 @@ struct in_addr {
> #define IP_PMTUDISC_DONT 0 /* Never send DF frames */
> #define IP_PMTUDISC_WANT 1 /* Use per route hints */
> #define IP_PMTUDISC_DO 2 /* Always DF */
> +#define IP_PMTUDISC_PROBE 3 /* Ignore dst pmtu */
>
> #define IP_MULTICAST_IF 32
> #define IP_MULTICAST_TTL 33
> diff --git a/include/linux/in6.h b/include/linux/in6.h
> index 4e8350a..d559fac 100644
> --- a/include/linux/in6.h
> +++ b/include/linux/in6.h
> @@ -179,6 +179,7 @@ struct in6_flowlabel_req
> #define IPV6_PMTUDISC_DONT 0
> #define IPV6_PMTUDISC_WANT 1
> #define IPV6_PMTUDISC_DO 2
> +#define IPV6_PMTUDISC_PROBE 3
>
> /* Flowlabel */
> #define IPV6_FLOWLABEL_MGR 32
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index 4ff3940..64038b4 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -284,7 +284,8 @@ struct sk_buff {
> nfctinfo:3;
> __u8 pkt_type:3,
> fclone:2,
> - ipvs_property:1;
> + ipvs_property:1,
> + ign_dst_mtu;
> __be16 protocol;
>
> void (*destructor)(struct sk_buff *skb);
> diff --git a/include/net/ip.h b/include/net/ip.h
> index e79c3e3..f5874a3 100644
> --- a/include/net/ip.h
> +++ b/include/net/ip.h
> @@ -201,7 +201,7 @@ int ip_decrease_ttl(struct iphdr *iph)
> static inline
> int ip_dont_fragment(struct sock *sk, struct dst_entry *dst)
> {
> - return (inet_sk(sk)->pmtudisc == IP_PMTUDISC_DO ||
> + return (inet_sk(sk)->pmtudisc >= IP_PMTUDISC_DO ||
> (inet_sk(sk)->pmtudisc == IP_PMTUDISC_WANT &&
> !(dst_metric(dst, RTAX_LOCK)&(1<<RTAX_MTU))));
> }
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index 702fa8f..5c8515c 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -474,6 +474,7 @@ struct sk_buff *skb_clone(struct sk_buff *skb, gfp_t gfp_mask)
> #if defined(CONFIG_IP_VS) || defined(CONFIG_IP_VS_MODULE)
> C(ipvs_property);
> #endif
> + C(ign_dst_mtu);
> C(protocol);
> n->destructor = NULL;
> C(mark);
> @@ -549,6 +550,7 @@ static void copy_skb_header(struct sk_buff *new, const struct sk_buff *old)
> #if defined(CONFIG_IP_VS) || defined(CONFIG_IP_VS_MODULE)
> new->ipvs_property = old->ipvs_property;
> #endif
> + new->ign_dst_mtu = old->ign_dst_mtu;
> #ifdef CONFIG_BRIDGE_NETFILTER
> new->nf_bridge = old->nf_bridge;
> nf_bridge_get(old->nf_bridge);
> diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
> index 90bdd53..a7e8944 100644
> --- a/net/ipv4/ip_output.c
> +++ b/net/ipv4/ip_output.c
> @@ -201,7 +201,8 @@ static inline int ip_finish_output(struct sk_buff *skb)
> return dst_output(skb);
> }
> #endif
> - if (skb->len > dst_mtu(skb->dst) && !skb_is_gso(skb))
> + if (skb->len > dst_mtu(skb->dst) &&
> + !skb->ign_dst_mtu && !skb_is_gso(skb))
> return ip_fragment(skb, ip_finish_output2);
> else
> return ip_finish_output2(skb);
> @@ -801,7 +802,9 @@ int ip_append_data(struct sock *sk,
> inet->cork.addr = ipc->addr;
> }
> dst_hold(&rt->u.dst);
> - inet->cork.fragsize = mtu = dst_mtu(rt->u.dst.path);
> + inet->cork.fragsize = mtu = inet->pmtudisc == IP_PMTUDISC_PROBE ?
> + rt->u.dst.dev->mtu :
> + dst_mtu(rt->u.dst.path);
> inet->cork.rt = rt;
> inet->cork.length = 0;
> sk->sk_sndmsg_page = NULL;
> @@ -1220,13 +1223,16 @@ int ip_push_pending_frames(struct sock *sk)
> * to fragment the frame generated here. No matter, what transforms
> * how transforms change size of the packet, it will come out.
> */
> - if (inet->pmtudisc != IP_PMTUDISC_DO)
> + if (inet->pmtudisc < IP_PMTUDISC_DO)
> skb->local_df = 1;
>
> + if (inet->pmtudisc == IP_PMTUDISC_PROBE)
> + skb->ign_dst_mtu = 1;
> +
> /* DF bit is set when we want to see DF on outgoing frames.
> * If local_df is set too, we still allow to fragment this frame
> * locally. */
> - if (inet->pmtudisc == IP_PMTUDISC_DO ||
> + if (inet->pmtudisc >= IP_PMTUDISC_DO ||
> (skb->len <= dst_mtu(&rt->u.dst) &&
> ip_dont_fragment(sk, &rt->u.dst)))
> df = htons(IP_DF);
> diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
> index 23048d9..98fa088 100644
> --- a/net/ipv4/ip_sockglue.c
> +++ b/net/ipv4/ip_sockglue.c
> @@ -536,7 +536,7 @@ static int do_ip_setsockopt(struct sock *sk, int level,
> inet->hdrincl = val ? 1 : 0;
> break;
> case IP_MTU_DISCOVER:
> - if (val<0 || val>2)
> + if (val<0 || val>3)
> goto e_inval;
> inet->pmtudisc = val;
> break;
> diff --git a/net/ipv4/raw.c b/net/ipv4/raw.c
> index f252f4e..f562262 100644
> --- a/net/ipv4/raw.c
> +++ b/net/ipv4/raw.c
> @@ -302,6 +302,9 @@ static int raw_send_hdrinc(struct sock *sk, void *from, size_t length,
> if (err)
> goto error_fault;
>
> + if (inet->pmtudisc == IP_PMTUDISC_PROBE)
> + skb->ign_dst_mtu = 1;
> +
> /* We don't modify invalid header */
> if (length >= sizeof(*iph) && iph->ihl * 4U <= length) {
> if (!iph->saddr)
> diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
> index 711dfc3..8b8c04b 100644
> --- a/net/ipv6/ip6_output.c
> +++ b/net/ipv6/ip6_output.c
> @@ -139,8 +139,8 @@ static int ip6_output2(struct sk_buff *skb)
>
> int ip6_output(struct sk_buff *skb)
> {
> - if ((skb->len > dst_mtu(skb->dst) && !skb_is_gso(skb)) ||
> - dst_allfrag(skb->dst))
> + if ((skb->len > dst_mtu(skb->dst) && !skb->ign_dst_mtu &&
> + !skb_is_gso(skb)) || dst_allfrag(skb->dst))
> return ip6_fragment(skb, ip6_output2);
> else
> return ip6_output2(skb);
> @@ -574,7 +574,7 @@ static int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
> hlen = ip6_find_1stfragopt(skb, &prevhdr);
> nexthdr = *prevhdr;
>
> - mtu = dst_mtu(&rt->u.dst);
> + mtu = skb->ign_dst_mtu ? skb->len : dst_mtu(&rt->u.dst);
> if (np && np->frag_size < mtu) {
> if (np->frag_size)
> mtu = np->frag_size;
> @@ -1015,7 +1015,8 @@ int ip6_append_data(struct sock *sk, int getfrag(void *from, char *to,
> inet->cork.fl = *fl;
> np->cork.hop_limit = hlimit;
> np->cork.tclass = tclass;
> - mtu = dst_mtu(rt->u.dst.path);
> + mtu = np->pmtudisc == IPV6_PMTUDISC_PROBE ?
> + rt->u.dst.dev->mtu : dst_mtu(rt->u.dst.path);
> if (np->frag_size < mtu) {
> if (np->frag_size)
> mtu = np->frag_size;
> @@ -1303,6 +1304,9 @@ int ip6_push_pending_frames(struct sock *sk)
> tmp_skb->sk = NULL;
> }
>
> + if (np->pmtudisc == IPV6_PMTUDISC_PROBE)
> + skb->ign_dst_mtu = 1;
> +
> ipv6_addr_copy(final_dst, &fl->fl6_dst);
> __skb_pull(skb, skb->h.raw - skb->nh.raw);
> if (opt && opt->opt_flen)
> diff --git a/net/ipv6/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c
> index f5f9582..6e88597 100644
> --- a/net/ipv6/ipv6_sockglue.c
> +++ b/net/ipv6/ipv6_sockglue.c
> @@ -694,7 +694,7 @@ done:
> retv = ip6_ra_control(sk, val, NULL);
> break;
> case IPV6_MTU_DISCOVER:
> - if (val<0 || val>2)
> + if (val<0 || val>3)
> goto e_inval;
> np->pmtudisc = val;
> retv = 0;
> diff --git a/net/ipv6/raw.c b/net/ipv6/raw.c
> index 75db277..9ef0946 100644
> --- a/net/ipv6/raw.c
> +++ b/net/ipv6/raw.c
> @@ -587,6 +587,9 @@ static int rawv6_send_hdrinc(struct sock *sk, void *from, int length,
> if (err)
> goto error_fault;
>
> + if (np->pmtudisc == IPV6_PMTUDISC_PROBE)
> + skb->ign_dst_mtu = 1;
> +
> IP6_INC_STATS(rt->rt6i_idev, IPSTATS_MIB_OUTREQUESTS);
> err = NF_HOOK(PF_INET6, NF_IP6_LOCAL_OUT, skb, NULL, rt->u.dst.dev,
> dst_output);
> --
> 1.5.0.2.gc260-dirty
>
> -
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