ipv6: rpl: Remove pskb(_may)?_pull() in ipv6_rpl_srh_rcv().

As Eric Dumazet pointed out [0], ipv6_rthdr_rcv() pulls these data

- Segment Routing Header : 8
- Hdr Ext Len : skb_transport_header(skb)[1] << 3

needed by ipv6_rpl_srh_rcv(). We can remove pskb_may_pull() and
replace pskb_pull() with skb_pull() in ipv6_rpl_srh_rcv().

Link: https://lore.kernel.org/netdev/CANn89iLboLwLrHXeHJucAqBkEL_S0rJFog68t7wwwXO-aNf5Mg@mail.gmail.com/ [0]
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net: rpl: fix rpl header size calculation

This patch fixes a missing 8 byte for the header size calculation. The
ipv6_rpl_srh_size() is used to check a skb_pull() on skb->data which
points to skb_transport_header(). Currently we only check on the
calculated addresses fields using CmprI and CmprE fields, see:

https://www.rfc-editor.org/rfc/rfc6554#section-3

there is however a missing 8 byte inside the calculation which stands
for the fields before the addresses field. Those 8 bytes are represented
by sizeof(struct ipv6_rpl_sr_hdr) expression.

Fixes: 8610c7c6e3bd ("net: ipv6: add support for rpl sr exthdr")
Signed-off-by: Alexander Aring <aahringo@redhat.com>
Reported-by: maxpl0it <maxpl0it@protonmail.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: ipv6: rpl*: Fix strange kerneldoc warnings due to bad header

net/ipv6/rpl_iptunnel.c:15: warning: cannot understand function prototype: 'struct rpl_iptunnel_encap '

The header on the file containing the author copyright message uses
kerneldoc /** opener. This confuses the parser when it gets to

struct rpl_iptunnel_encap {
struct ipv6_rpl_sr_hdr srh[0];
};

Similarly:

net//ipv6/rpl.c:10: warning: Function parameter or member 'x' not described in 'IPV6_PFXTAIL_LEN'

where IPV6_PFXTAIL_LEN is a macro definition, not a function.

Convert the header comments to a plain /* comment.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lore.kernel.org/r/20201028013123.931816-1-andrew@lunn.ch
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

ipv6: rpl: fix full address compression

This patch makes it impossible that cmpri or cmpre values are set to the
value 16 which is not possible, because these are 4 bit values. We
currently run in an overflow when assigning the value 16 to it.

According to the standard a value of 16 can be interpreted as a full
elided address which isn't possible to set as compression value. A reason
why this cannot be set is that the current ipv6 header destination address
should never show up inside the segments of the rpl header. In this case we
run in a overflow and the address will have no compression at all. Means
cmpri or compre is set to 0.

As we handle cmpri and cmpre sometimes as unsigned char or 4 bit value
inside the rpl header the current behaviour ends in an invalid header
format. This patch simple use the best compression method if we ever run
into the case that the destination address is showed up inside the rpl
segments. We avoid the overflow handling and the rpl header is still valid,
even when we have the destination address inside the rpl segments.

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

ipv6: rpl: fix loop iteration

This patch fix the loop iteration by not walking over the last
iteration. The cmpri compressing value exempt the last segment. As the
code shows the last iteration will be overwritten by cmpre value
handling which is for the last segment.

I think this doesn't end in any bufferoverflows because we work on worst
case temporary buffer sizes but it ends in not best compression settings
in some cases.

Fixes: 8610c7c6e3bd ("net: ipv6: add support for rpl sr exthdr")
Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: ipv6: add support for rpl sr exthdr

This patch adds rpl source routing receive handling. Everything works
only if sysconf "rpl_seg_enabled" and source routing is enabled. Mostly
the same behaviour as IPv6 segmentation routing. To handle compression
and uncompression a rpl.c file is created which contains the necessary
functionality. The receive handling will also care about IPv6
encapsulated so far it's specified as possible nexthdr in RFC 6554.

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>