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sctp: Use m_apply() to calcuate a checksum for an mbuf chain

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m_apply() works on unmapped mbufs, so this will let us elide
mb_unmapped_to_ext() calls preceding sctp_calculate_cksum() calls in
the network stack.

Modify sctp_calculate_cksum() to assume it's passed an mbuf header.
This assumption appears to be true in practice, and we need to know the
full length of the chain.

No functional change intended.

Reviewed by:	tuexen, jhb
MFC after:	2 weeks
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D32941
This commit is contained in:
Mark Johnston 2021-11-16 13:36:30 -05:00
parent fcaa890c44
commit b4d758a0cc
1 changed files with 20 additions and 23 deletions
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43
sys/netinet/sctp_crc32.c
View File

@ -80,6 +80,16 @@ sctp_finalize_crc32c(uint32_t crc32c)
return (crc32c);
}
static int
sctp_calculate_cksum_cb(void *arg, void *data, u_int len)
{
uint32_t *basep;
basep = arg;
*basep = calculate_crc32c(*basep, data, len);
return (0);
}
/*
* Compute the SCTP checksum in network byte order for a given mbuf chain m
* which contains an SCTP packet starting at offset.
@ -89,30 +99,17 @@ sctp_finalize_crc32c(uint32_t crc32c)
uint32_t
sctp_calculate_cksum(struct mbuf *m, uint32_t offset)
{
uint32_t base = 0xffffffff;
uint32_t base;
int len;
while (offset > 0) {
KASSERT(m != NULL, ("sctp_calculate_cksum, offset > length of mbuf chain"));
if (offset < (uint32_t)m->m_len) {
break;
}
offset -= m->m_len;
m = m->m_next;
}
if (offset > 0) {
base = calculate_crc32c(base,
(unsigned char *)(m->m_data + offset),
(unsigned int)(m->m_len - offset));
m = m->m_next;
}
while (m != NULL) {
base = calculate_crc32c(base,
(unsigned char *)m->m_data,
(unsigned int)m->m_len);
m = m->m_next;
}
base = sctp_finalize_crc32c(base);
return (base);
M_ASSERTPKTHDR(m);
KASSERT(offset < m->m_pkthdr.len,
("%s: invalid offset %u into mbuf %p", __func__, offset, m));
base = 0xffffffff;
len = m->m_pkthdr.len - offset;
(void)m_apply(m, offset, len, sctp_calculate_cksum_cb, &base);
return (sctp_finalize_crc32c(base));
}
#if defined(SCTP) || defined(SCTP_SUPPORT)