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Add comments to hard-to-follow File descriptor handling code

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julian 1996-12-05 22:41:13 +00:00
parent 600376a35c
commit ed6626ac57
1 changed files with 68 additions and 1 deletions
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69
sys/kern/uipc_usrreq.c
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@ -31,7 +31,7 @@
* SUCH DAMAGE.
*
* From: @(#)uipc_usrreq.c 8.3 (Berkeley) 1/4/94
* $Id: uipc_usrreq.c,v 1.14 1996/03/11 02:17:11 hsu Exp $
* $Id: uipc_usrreq.c,v 1.15 1996/03/11 15:12:47 davidg Exp $
*/
#include <sys/param.h>
@ -658,6 +658,9 @@ unp_externalize(rights)
int newfds = (cm->cmsg_len - sizeof(*cm)) / sizeof (int);
int f;
/*
* if the new FD's will not fit, then we free them all
*/
if (!fdavail(p, newfds)) {
for (i = 0; i < newfds; i++) {
fp = *rp;
@ -666,6 +669,12 @@ unp_externalize(rights)
}
return (EMSGSIZE);
}
/*
* now change each pointer to an fd in the global table to
* an integer that is the index to the local fd table entry
* that we set up to point to the global one we are transferring.
* XXX this assumes a pointer and int are the same size...!
*/
for (i = 0; i < newfds; i++) {
if (fdalloc(p, 0, &f))
panic("unp_externalize");
@ -694,6 +703,10 @@ unp_internalize(control, p)
cm->cmsg_len != control->m_len)
return (EINVAL);
oldfds = (cm->cmsg_len - sizeof (*cm)) / sizeof (int);
/*
* check that all the FDs passed in refer to legal OPEN files
* If not, reject the entire operation.
*/
rp = (struct file **)(cm + 1);
for (i = 0; i < oldfds; i++) {
fd = *(int *)rp++;
@ -701,6 +714,11 @@ unp_internalize(control, p)
fdp->fd_ofiles[fd] == NULL)
return (EBADF);
}
/*
* Now replace the integer FDs with pointers to
* the associated global file table entry..
* XXX this assumes a pointer and an int are the same size!
*/
rp = (struct file **)(cm + 1);
for (i = 0; i < oldfds; i++) {
fp = fdp->fd_ofiles[*(int *)rp];
@ -726,22 +744,52 @@ unp_gc()
return;
unp_gcing = 1;
unp_defer = 0;
/*
* before going through all this, set all FDs to
* be NOT defered and NOT externally accessible
*/
for (fp = filehead.lh_first; fp != 0; fp = fp->f_list.le_next)
fp->f_flag &= ~(FMARK|FDEFER);
do {
for (fp = filehead.lh_first; fp != 0; fp = fp->f_list.le_next) {
/*
* If the file is not open, skip it
*/
if (fp->f_count == 0)
continue;
/*
* If we already marked it as 'defer' in a
* previous pass, then try process it this time
* and un-mark it
*/
if (fp->f_flag & FDEFER) {
fp->f_flag &= ~FDEFER;
unp_defer--;
} else {
/*
* if it's not defered, then check if it's
* already marked.. if so skip it
*/
if (fp->f_flag & FMARK)
continue;
/*
* If all references are from messages
* in transit, then skip it. it's not
* externally accessible.
*/
if (fp->f_count == fp->f_msgcount)
continue;
/*
* If it got this far then it must be
* externally accessible.
*/
fp->f_flag |= FMARK;
}
/*
* either it was defered, or it is externally
* accessible and not already marked so.
* Now check if it is possibly one of OUR sockets.
*/
if (fp->f_type != DTYPE_SOCKET ||
(so = (struct socket *)fp->f_data) == 0)
continue;
@ -764,6 +812,13 @@ unp_gc()
goto restart;
}
#endif
/*
* So, Ok, it's one of our sockets and it IS externally
* accessible (or was defered). Now we look
* to see if we hold any file descriptors in it's
* message buffers. Follow those links and mark them
* as accessible too.
*/
unp_scan(so->so_rcv.sb_mb, unp_mark);
}
} while (unp_defer);
@ -810,14 +865,26 @@ unp_gc()
for (nunref = 0, fp = filehead.lh_first, fpp = extra_ref; fp != 0;
fp = nextfp) {
nextfp = fp->f_list.le_next;
/*
* If it's not open, skip it
*/
if (fp->f_count == 0)
continue;
/*
* If all refs are from msgs, and it's not marked accessible
* then it must be referenced from some unreachable cycle
* of (shut-down) FDs, so include it in our
* list of FDs to remove
*/
if (fp->f_count == fp->f_msgcount && !(fp->f_flag & FMARK)) {
*fpp++ = fp;
nunref++;
fp->f_count++;
}
}
/*
* for each FD on our hit list, do the following two things
*/
for (i = nunref, fpp = extra_ref; --i >= 0; ++fpp)
sorflush((struct socket *)(*fpp)->f_data);
for (i = nunref, fpp = extra_ref; --i >= 0; ++fpp)