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mbuf(9): unbreak m_fragment()

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- Fix it by replacing m_cat() with m_prev->m_next = m_new
(m_cat() will try to append data - as a result, there will be no
fragmentation).
- Move some constants out of the loop.

Was previously tested with D4077.

Differential Revision:	https://reviews.freebsd.org/D4090
This commit is contained in:
Andriy Voskoboinyk 2017-10-16 21:46:11 +00:00
parent c64c1f95a7
commit 6623429867
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=324673
1 changed files with 27 additions and 30 deletions
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57
sys/kern/uipc_mbuf.c
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@ -1449,62 +1449,59 @@ m_collapse(struct mbuf *m0, int how, int maxfrags)
struct mbuf *
m_fragment(struct mbuf *m0, int how, int length)
{
struct mbuf *m_new = NULL, *m_final = NULL;
int progress = 0;
struct mbuf *m_first, *m_last;
int divisor = 255, progress = 0, fraglen;
if (!(m0->m_flags & M_PKTHDR))
return (m0);
if ((length == 0) || (length < -2))
if (length == 0 || length < -2)
return (m0);
if (length > MCLBYTES)
length = MCLBYTES;
if (length < 0 && divisor > MCLBYTES)
divisor = MCLBYTES;
if (length == -1)
length = 1 + (arc4random() % divisor);
if (length > 0)
fraglen = length;
m_fixhdr(m0); /* Needed sanity check */
m_final = m_getcl(how, MT_DATA, M_PKTHDR);
if (m_final == NULL)
m_first = m_getcl(how, MT_DATA, M_PKTHDR);
if (m_first == NULL)
goto nospace;
if (m_dup_pkthdr(m_final, m0, how) == 0)
if (m_dup_pkthdr(m_first, m0, how) == 0)
goto nospace;
m_new = m_final;
if (length == -1)
length = 1 + (arc4random() & 255);
m_last = m_first;
while (progress < m0->m_pkthdr.len) {
int fraglen;
if (length > 0)
fraglen = length;
else
fraglen = 1 + (arc4random() & 255);
if (length == -2)
fraglen = 1 + (arc4random() % divisor);
if (fraglen > m0->m_pkthdr.len - progress)
fraglen = m0->m_pkthdr.len - progress;
if (fraglen > MCLBYTES)
fraglen = MCLBYTES;
if (m_new == NULL) {
m_new = m_getcl(how, MT_DATA, 0);
if (progress != 0) {
struct mbuf *m_new = m_getcl(how, MT_DATA, 0);
if (m_new == NULL)
goto nospace;
m_last->m_next = m_new;
m_last = m_new;
}
m_copydata(m0, progress, fraglen, mtod(m_new, caddr_t));
m_copydata(m0, progress, fraglen, mtod(m_last, caddr_t));
progress += fraglen;
m_new->m_len = fraglen;
if (m_new != m_final)
m_cat(m_final, m_new);
m_new = NULL;
m_last->m_len = fraglen;
}
m_freem(m0);
m0 = m_final;
m0 = m_first;
return (m0);
nospace:
if (m_final)
m_freem(m_final);
if (m_first)
m_freem(m_first);
/* Return the original chain on failure */
return (m0);
}