On Wed, May 6, 2020 at 7:42 PM Eric Dumazet <eric.duma...@gmail.com> wrote:
>
>
>
> On 5/5/20 9:05 AM, William Tu wrote:
> > The Type I ERSPAN frame format is based on the barebones
> > IP + GRE(4-byte) encapsulation on top of the raw mirrored frame.
> > Both type I and II use 0x88BE as protocol type. Unlike type II
> > and III, no sequence number or key is required.
> > To creat a type I erspan tunnel device:
> > $ ip link add dev erspan11 type erspan \
> > local 172.16.1.100 remote 172.16.1.200 \
> > erspan_ver 0
> >
> > Signed-off-by: William Tu <u9012...@gmail.com>
> > ---
> > v2:
> > remove the inline keyword, let compiler decide.
> > v1:
> > I didn't notice there is Type I when I did first erspan implementation
> > because it is not in the ietf draft 00 and 01. It's until recently I got
> > request for adding type I. Spec is below at draft 02:
> > https://tools.ietf.org/html/draft-foschiano-erspan-02#section-4.1
> >
> > To verify with Wireshark, make sure you have:
> > commit ef76d65fc61d01c2ce5184140f4b1bba0019078b
> > Author: Guy Harris <g...@alum.mit.edu>
> > Date: Mon Sep 30 16:35:35 2019 -0700
> >
> > Fix checks for "do we have an ERSPAN header?"
> > ---
> > include/net/erspan.h | 19 +++++++++++++++--
> > net/ipv4/ip_gre.c | 58
> > ++++++++++++++++++++++++++++++++++++++--------------
> > 2 files changed, 60 insertions(+), 17 deletions(-)
> >
> > diff --git a/include/net/erspan.h b/include/net/erspan.h
> > index b39643ef4c95..0d9e86bd9893 100644
> > --- a/include/net/erspan.h
> > +++ b/include/net/erspan.h
> > @@ -2,7 +2,19 @@
> > #define __LINUX_ERSPAN_H
> >
> > /*
> > - * GRE header for ERSPAN encapsulation (8 octets [34:41]) -- 8 bytes
> > + * GRE header for ERSPAN type I encapsulation (4 octets [34:37])
> > + * 0 1 2 3
> > + * 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
> > + * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> > + * |0|0|0|0|0|00000|000000000|00000| Protocol Type for ERSPAN |
> > + * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> > + *
> > + * The Type I ERSPAN frame format is based on the barebones IP + GRE
> > + * encapsulation (as described above) on top of the raw mirrored frame.
> > + * There is no extra ERSPAN header.
> > + *
> > + *
> > + * GRE header for ERSPAN type II and II encapsulation (8 octets [34:41])
> > * 0 1 2 3
> > * 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
> > * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> > @@ -43,7 +55,7 @@
> > * | Platform Specific Info |
> > * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> > *
> > - * GRE proto ERSPAN type II = 0x88BE, type III = 0x22EB
> > + * GRE proto ERSPAN type I/II = 0x88BE, type III = 0x22EB
> > */
> >
> > #include <uapi/linux/erspan.h>
> > @@ -139,6 +151,9 @@ static inline u8 get_hwid(const struct erspan_md2 *md2)
> >
> > static inline int erspan_hdr_len(int version)
> > {
> > + if (version == 0)
> > + return 0;
> > +
> > return sizeof(struct erspan_base_hdr) +
> > (version == 1 ? ERSPAN_V1_MDSIZE : ERSPAN_V2_MDSIZE);
> > }
> > diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
> > index 029b24eeafba..e29cd48674d7 100644
> > --- a/net/ipv4/ip_gre.c
> > +++ b/net/ipv4/ip_gre.c
> > @@ -248,6 +248,15 @@ static void gre_err(struct sk_buff *skb, u32 info)
> > ipgre_err(skb, info, &tpi);
> > }
> >
> > +static bool is_erspan_type1(int gre_hdr_len)
> > +{
> > + /* Both ERSPAN type I (version 0) and type II (version 1) use
> > + * protocol 0x88BE, but the type I has only 4-byte GRE header,
> > + * while type II has 8-byte.
> > + */
> > + return gre_hdr_len == 4;
> > +}
> > +
> > static int erspan_rcv(struct sk_buff *skb, struct tnl_ptk_info *tpi,
> > int gre_hdr_len)
> > {
> > @@ -262,17 +271,26 @@ static int erspan_rcv(struct sk_buff *skb, struct
> > tnl_ptk_info *tpi,
> > int len;
> >
> > itn = net_generic(net, erspan_net_id);
> > -
> > iph = ip_hdr(skb);
> > - ershdr = (struct erspan_base_hdr *)(skb->data + gre_hdr_len);
> > - ver = ershdr->ver;
> > -
> > - tunnel = ip_tunnel_lookup(itn, skb->dev->ifindex,
> > - tpi->flags | TUNNEL_KEY,
> > - iph->saddr, iph->daddr, tpi->key);
> > + if (is_erspan_type1(gre_hdr_len)) {
> > + ver = 0;
> > + tunnel = ip_tunnel_lookup(itn, skb->dev->ifindex,
> > + tpi->flags | TUNNEL_NO_KEY,
> > + iph->saddr, iph->daddr, 0);
> > + } else {
> > + ershdr = (struct erspan_base_hdr *)(skb->data + gre_hdr_len);
> > + ver = ershdr->ver;
> > + tunnel = ip_tunnel_lookup(itn, skb->dev->ifindex,
> > + tpi->flags | TUNNEL_KEY,
> > + iph->saddr, iph->daddr, tpi->key);
> > + }
> >
> > if (tunnel) {
> > - len = gre_hdr_len + erspan_hdr_len(ver);
> > + if (is_erspan_type1(gre_hdr_len))
> > + len = gre_hdr_len;
> > + else
> > + len = gre_hdr_len + erspan_hdr_len(ver);
> > +
> > if (unlikely(!pskb_may_pull(skb, len)))
> > return PACKET_REJECT;
> >
> > @@ -665,7 +683,10 @@ static netdev_tx_t erspan_xmit(struct sk_buff *skb,
> > }
> >
> > /* Push ERSPAN header */
> > - if (tunnel->erspan_ver == 1) {
> > + if (tunnel->erspan_ver == 0) {
> > + proto = htons(ETH_P_ERSPAN);
> > + tunnel->parms.o_flags &= ~TUNNEL_SEQ;
> > + } else if (tunnel->erspan_ver == 1) {
> > erspan_build_header(skb, ntohl(tunnel->parms.o_key),
> > tunnel->index,
> > truncate, true);
> > @@ -1066,7 +1087,10 @@ static int erspan_validate(struct nlattr *tb[],
> > struct nlattr *data[],
> > if (ret)
> > return ret;
> >
> > - /* ERSPAN should only have GRE sequence and key flag */
> > + if (nla_get_u8(data[IFLA_GRE_ERSPAN_VER]) == 0)
>
> I do not see anything in the code making sure IFLA_GRE_ERSPAN_VER has been
> provided by the user ?
>
Hi Eric,
Thanks! at the iproute2 we always set the IFLA_GRE_ERSPAN_VER to 1 as
default when user
doesn't specify. But I should also make sure it is checked here for
non-iproute2 users.
If I understand correctly, I should add
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -1087,7 +1087,7 @@ static int erspan_validate(struct nlattr *tb[],
struct nlattr *data[],
if (ret)
return ret;
- if (nla_get_u8(data[IFLA_GRE_ERSPAN_VER]) == 0)
+ if (data[IFLA_GRE_ERSPAN_VER] &&
nla_get_u8(data[IFLA_GRE_ERSPAN_VER]) == 0)
return 0;
/* ERSPAN type II/III should only have GRE sequence and key flag */
Regards,
William
