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sctp: introduce sctp_mtu_payload

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When given a MTU, this function calculates how much payload we can carry
on it. Without a MTU, it calculates the amount of header overhead we
have.

So that when we have extra overhead, like the one added for IP options
on SELinux patches, it is easier to handle it.

Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Marcelo Ricardo Leitner 2018-04-26 16:58:54 -03:00 • committed by David S. Miller
parent c4b2893dae
commit feddd6c1af
3 changed files with 31 additions and 20 deletions
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19
include/net/sctp/sctp.h
View file

@ -607,6 +607,25 @@ static inline struct dst_entry *sctp_transport_dst_check(struct sctp_transport *
return t->dst;
}
/* Calculate max payload size given a MTU, or the total overhead if
* given MTU is zero
*/
static inline __u32 sctp_mtu_payload(const struct sctp_sock *sp,
__u32 mtu, __u32 extra)
{
__u32 overhead = sizeof(struct sctphdr) + extra;
if (sp)
overhead += sp->pf->af->net_header_len;
else
overhead += sizeof(struct ipv6hdr);
if (WARN_ON_ONCE(mtu && mtu <= overhead))
mtu = overhead;
return mtu ? mtu - overhead : overhead;
}
static inline bool sctp_transport_pmtu_check(struct sctp_transport *t)
{
__u32 pmtu = max_t(size_t, SCTP_TRUNC4(dst_mtu(t->dst)),