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iauth: harden poll FD handling and recovery #91

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iauth: harden poll FD handling and recovery
patrick-irc Oct 12, 2026
7e856c0
Merge branch '2.12.0' into iauth_poll_fd_recovery
patrick-irc Oct 13, 2026
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221 changes: 180 additions & 41 deletions iauth/a_io.c
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Original file line number Diff line number Diff line change
Expand Up @@ -29,9 +29,6 @@ static const volatile char rcsid[] = "@(#)$Id: a_io.c,v 1.31 2005/01/03 17:33:55

anAuthData cldata[MAXCONNECTIONS]; /* index == ircd fd */
static int cl_highest = -1;
#if defined(USE_POLL)
static int fd2cl[MAXCONNECTIONS]; /* fd -> cl mapping */
#endif

#define IOBUFSIZE 4096
static char iobuf[IOBUFSIZE+1];
Expand Down Expand Up @@ -939,14 +936,27 @@ void loop_io(void)
# define TST_READ_EVENT( thisfd ) pfd->revents & POLLREADFLAGS
# define TST_WRITE_EVENT( thisfd ) pfd->revents & POLLWRITEFLAGS

# define CHECK_PFD( thisfd ) \
if ( pfd->fd != thisfd ) { \
pfd = &poll_fdarray[nbr_pfds++];\
pfd->fd = thisfd; \
pfd->events = 0; \
}

struct pollfd poll_fdarray[MAXCONNECTIONS];
/* One poll slot per client, global FD and the ircd stream (fd 0). */
# define IAUTH_MAX_POLL_FDS (MAXCONNECTIONS + MAXGFD + 1)
# define CHECK_PFD( thisfd ) \
do { \
if (pfd->fd != (thisfd)) { \
if (nbr_pfds >= IAUTH_MAX_POLL_FDS) { \
sendto_log(ALOG_IRCD, LOG_CRIT, \
"io_loop(): poll FD limit exceeded"); \
return; \
} \
pfd = &poll_fdarray[nbr_pfds++]; \
pfd->fd = (thisfd); \
pfd->events = 0; \
} \
} while (0)

static struct pollfd poll_fdarray[IAUTH_MAX_POLL_FDS];
static int poll_to_cl[IAUTH_MAX_POLL_FDS]; /* poll slot -> client */
static AnInstance *resume_inst[MAXCONNECTIONS];
static unsigned char need_clean[MAXCONNECTIONS];
static unsigned char bad_global[MAXGFD];
struct pollfd * pfd = poll_fdarray;
int nbr_pfds = 0;
#endif
Expand Down Expand Up @@ -1001,9 +1011,9 @@ void loop_io(void)
}
}
}
/* reset fd->client mapping: global FDs remain -1 */
for (i = 0; i < MAXCONNECTIONS; i++)
fd2cl[i] = -1;
/* A descriptor number need not be less than MAXCONNECTIONS. */
for (i = 0; i < IAUTH_MAX_POLL_FDS; i++)
poll_to_cl[i] = -1;
#endif
for (i = 0; i <= cl_highest; i++)
{
Expand All @@ -1023,7 +1033,7 @@ void loop_io(void)
if (cldata[i].rfd > highfd)
highfd = cldata[i].rfd;
#else
fd2cl[cldata[i].rfd] = i;
poll_to_cl[pfd - poll_fdarray] = i;
#endif
nfds++;
}
Expand All @@ -1034,7 +1044,7 @@ void loop_io(void)
if (cldata[i].wfd > highfd)
highfd = cldata[i].wfd;
#else
fd2cl[cldata[i].wfd] = i;
poll_to_cl[pfd - poll_fdarray] = i;
#endif
nfds++;
}
Expand Down Expand Up @@ -1072,6 +1082,153 @@ void loop_io(void)
if (nfds == 0) /* end of timeout */
return;

#if defined(USE_POLL)
/*
* Only poll slots, never numeric file descriptors, index these tables.
* Keep the recovery lists static to avoid large per-call stack frames.
*/
if (poll_fdarray[0].revents & POLLNVAL)
{
sendto_log(ALOG_IRCD, LOG_CRIT,
"io_loop(): ircd stream has an invalid FD");
exit(1);
}

bzero((char *) resume_inst, sizeof(resume_inst));
bzero((char *) need_clean, sizeof(need_clean));
bzero((char *) bad_global, sizeof(bad_global));

/*
* Phase 1: snapshot all invalid descriptors and clear stale client
* references BEFORE running a callback that might allocate a new FD.
*/
for (pf = poll_fdarray + 1; pf < poll_fdarray + nbr_pfds; ++pf)
{
if (!(pf->revents & POLLNVAL))
continue;

i = poll_to_cl[pf - poll_fdarray];
if (i >= 0 && i <= cl_highest && cldata[i].instance &&
(cldata[i].rfd == pf->fd || cldata[i].wfd == pf->fd))
{
resume_inst[i] = cldata[i].instance;
need_clean[i] = 1;
if (cldata[i].rfd == pf->fd)
cldata[i].rfd = 0;
if (cldata[i].wfd == pf->fd)
cldata[i].wfd = 0;
sendto_log(ALOG_IRCD, LOG_WARNING,
"io_loop(): invalid FD %d for client %d", pf->fd, i);
}
else
{
for (gi = 0; gi < MAXGFD; ++gi)
if (gfd_used(gi) && gfdv[gi].fd == pf->fd)
bad_global[gi] = 1;
}
pf->revents = 0;
nfds--;
}

/*
* Phase 2a: a failed global socket invalidates the current module's
* outstanding requests. Apply the module's timeout policy BEFORE
* grelease() removes pending records, and collect clients for later
* scheduler resumption.
*/
for (gi = 0; gi < MAXGFD; ++gi)
{
AnInstance *inst;
int gj;

if (!bad_global[gi] || !gfd_used(gi))
continue;
inst = gfdv[gi].inst;
sendto_log(ALOG_IRCD, LOG_WARNING,
"io_loop(): invalid global module FD %d", gfdv[gi].fd);

/* Retire all ready events for this module's global sockets. */
for (gj = 0; gj < MAXGFD; ++gj)
{
if (!gfd_used(gj) || gfdv[gj].inst != inst)
continue;
for (pf = poll_fdarray + 1;
pf < poll_fdarray + nbr_pfds; ++pf)
{
if (pf->fd == gfdv[gj].fd && pf->revents)
{
pf->revents = 0;
nfds--;
}
}
}

for (i = 0; i <= cl_highest; ++i)
{
if (cldata[i].instance != inst)
continue;
resume_inst[i] = inst;
/* timeout() owns the module's success/failure policy and cleanup. */
if (inst->mod && inst->mod->timeout)
(void) inst->mod->timeout(i);
need_clean[i] = 0;
}
if (inst->mod && inst->mod->grelease)
inst->mod->grelease(inst);
else
io_unregister_gfd(inst);
}

/* Phase 2b: finish invalid per-client descriptors without starting the
* next module until every failed descriptor has been cleaned up. */
for (i = 0; i <= cl_highest; ++i)
{
AnInstance *inst = resume_inst[i];

if (!inst)
continue;
if (need_clean[i])
{
int done = 0;
if (!inst->mod)
{
sendto_log(ALOG_IRCD, LOG_CRIT,
"io_loop(): missing client module");
exit(1);
}
/* Apply the module's timeout/deny policy when a client FD is lost. */
if (inst->mod->timeout)
done = (inst->mod->timeout(i) != 0);
if (!done)
{
if (!inst->mod->clean)
{
sendto_log(ALOG_IRCD, LOG_CRIT,
"io_loop(): missing client cleanup callback");
exit(1);
}
inst->mod->clean(i);
}
}
/* Events for sockets closed by cleanup must not be dispatched. */
for (pf = poll_fdarray + 1; pf < poll_fdarray + nbr_pfds; ++pf)
{
if (poll_to_cl[pf - poll_fdarray] == i && pf->revents)
{
pf->revents = 0;
nfds--;
}
}
}

/* Phase 3: only now may next_io() open and reuse descriptor numbers. */
for (i = 0; i <= cl_highest; ++i)
{
if (resume_inst[i] && cldata[i].instance == resume_inst[i])
next_io(i, resume_inst[i]);
}
#endif

#if !defined(USE_POLL)
for (gi = 0; gi < MAXGFD; gi++)
{
Expand Down Expand Up @@ -1111,10 +1268,10 @@ void loop_io(void)
{
if (gfd_used(gi) && gfdv[gi].fd == fdj)
{
if (gfdv[gi].inst && gfdv[gi].inst->mod &&
gfdv[gi].inst->mod->gwork)
AnInstance *inst = gfdv[gi].inst;
if (inst->mod && inst->mod->gwork)
{
gfdv[gi].inst->mod->gwork(gfdv[gi].inst);
inst->mod->gwork(inst);
}
pf->revents = 0;
nfds--;
Expand All @@ -1135,29 +1292,11 @@ void loop_io(void)
#endif
{
#if defined(USE_POLL)
/* bounds check against fd2cl array and skip global FDs */
int fdj = pfd->fd;
/* fd outside mapping range -> not a client FD */
if (fdj < 0 || fdj >= MAXCONNECTIONS)
{
/* Ignore global, retired or re-used descriptors. */
i = poll_to_cl[pfd - poll_fdarray];
if (i < 0 || i > cl_highest || !cldata[i].instance ||
(cldata[i].rfd != pfd->fd && cldata[i].wfd != pfd->fd))
continue;
}
i = fd2cl[fdj];
/* global or unmapped FD -> already handled in global block */
if (i == -1)
{
continue;
}
#if defined(IAUTH_DEBUG)
/* sanity check: ensure client index is within valid range */
if (i < 0 || i > cl_highest)
{
sendto_log(ALOG_DALL, LOG_CRIT,
"io_loop(): fatal bug (invalid cl=%d fd=%d)", i,
fdj);
exit(1);
}
#endif
#endif
if (cldata[i].rfd <= 0 && cldata[i].wfd <= 0)
{
Expand Down
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