Introduce pipex_iterator(), the special thing to perform

`pipex_session_list' foreach walkthrough with `pipex_list_mtx' mutex(9)
relocking. It inserts special item after acquired `session' and keeps it
linked until `session' release. Only owner can unlink it's own item, so
the LIST_NEXT(session) is always valid even the `session' was unlinked.
The iterator skips special items at the `session' acquisition time, as
all other foreach loops where `pipex_list_mtx' mutex(9) is not relocked.

ok yasuoka

diff --git a/sys/net/pipex.c b/sys/net/pipex.c
index c6a4e27..ed038c1 100644 (file)
--- a/sys/net/pipex.c
+++ b/sys/net/pipex.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: pipex.c,v 1.152 2024/01/23 16:57:52 mvs Exp $ */
+/*     $OpenBSD: pipex.c,v 1.153 2024/01/23 17:57:21 mvs Exp $ */
 
 /*-
  * Copyright (c) 2009 Internet Initiative Japan Inc.
@@ -151,6 +151,8 @@ pipex_destroy_all_sessions(void *ownersc)
 
        LIST_FOREACH_SAFE(session, &pipex_session_list, session_list,
            session_tmp) {
+               if (session->flags & PIPEX_SFLAGS_ITERATOR)
+                       continue;
                if (session->ownersc == ownersc) {
                        KASSERT((session->flags & PIPEX_SFLAGS_PPPX) == 0);
                        pipex_unlink_session_locked(session);
@@ -594,6 +596,8 @@ pipex_get_closed(struct pipex_session_list_req *req, void *ownersc)
 
        LIST_FOREACH_SAFE(session, &pipex_close_wait_list, state_list,
            session_tmp) {
+               if (session->flags & PIPEX_SFLAGS_ITERATOR)
+                       continue;
                if (session->ownersc != ownersc)
                        continue;
                req->plr_ppp_id[req->plr_ppp_id_count++] = session->ppp_id;
@@ -730,6 +734,8 @@ pipex_timer(void *ignored_arg)
        /* walk through */
        LIST_FOREACH_SAFE(session, &pipex_session_list, session_list,
            session_tmp) {
+               if (session->flags & PIPEX_SFLAGS_ITERATOR)
+                       continue;
                switch (session->state) {
                case PIPEX_STATE_OPENED:
                        if (session->timeout_sec == 0)
@@ -769,6 +775,47 @@ pipex_timer(void *ignored_arg)
 /***********************************************************************
  * Common network I/O functions.  (tunnel protocol independent)
  ***********************************************************************/
+
+struct pipex_session *
+pipex_iterator(struct pipex_session *session,
+    struct pipex_session_iterator *iter, void *ownersc)
+{
+       struct pipex_session *session_tmp;
+
+       mtx_enter(&pipex_list_mtx);
+
+       if (session)
+               session_tmp = LIST_NEXT(session, session_list);
+       else
+               session_tmp = LIST_FIRST(&pipex_session_list);
+
+       while (session_tmp) {
+               if (session_tmp->flags & PIPEX_SFLAGS_ITERATOR)
+                       goto next;
+               if (session_tmp->ownersc != ownersc)
+                       goto next;
+               break;
+next:
+               session_tmp = LIST_NEXT(session_tmp, session_list);
+       }
+
+       if (session)
+               LIST_REMOVE(iter, session_list);
+
+       if (session_tmp) {
+               LIST_INSERT_AFTER(session_tmp,
+                   (struct pipex_session *)&iter, session_list);
+               refcnt_take(&session_tmp->pxs_refcnt);
+       }
+
+       mtx_leave(&pipex_list_mtx);
+
+       if (session)
+               pipex_rele_session(session);
+
+       return (session_tmp); 
+}
+
 void
 pipex_ip_output(struct mbuf *m0, struct pipex_session *session)
 {
@@ -803,23 +850,17 @@ pipex_ip_output(struct mbuf *m0, struct pipex_session *session)
 
                pipex_ppp_output(m0, session, PPP_IP);
        } else {
+               struct pipex_session_iterator iter = {
+                       .flags = PIPEX_SFLAGS_ITERATOR,
+               };
+
                struct pipex_session *session_tmp;
                struct mbuf *m;
 
                m0->m_flags &= ~(M_BCAST|M_MCAST);
 
-               mtx_enter(&pipex_list_mtx);
-
-               session_tmp = LIST_FIRST(&pipex_session_list);
-               while (session_tmp != NULL) {
-                       struct pipex_session *session_save = NULL;
-
-                       if (session_tmp->ownersc != session->ownersc)
-                               goto next;
-
-                       refcnt_take(&session_tmp->pxs_refcnt);
-                       mtx_leave(&pipex_list_mtx);
-
+               session_tmp = pipex_iterator(NULL, &iter, session->ownersc);
+               while (session_tmp) {
                        m = m_copym(m0, 0, M_COPYALL, M_NOWAIT);
                        if (m != NULL)
                                pipex_ppp_output(m, session_tmp, PPP_IP);
@@ -827,16 +868,10 @@ pipex_ip_output(struct mbuf *m0, struct pipex_session *session)
                                counters_inc(session_tmp->stat_counters,
                                    pxc_oerrors);
 
-                       mtx_enter(&pipex_list_mtx);
-                       session_save = session_tmp;
-next:
-                       session_tmp = LIST_NEXT(session_tmp, session_list);
-                       if (session_save != NULL)
-                               pipex_rele_session(session_save);
+                       session_tmp = pipex_iterator(session_tmp,
+                           &iter, session->ownersc);
                }
 
-               mtx_leave(&pipex_list_mtx);
-
                m_freem(m0);
        }
 

diff --git a/sys/net/pipex_local.h b/sys/net/pipex_local.h
index 8274bdc..01b7c45 100644 (file)
--- a/sys/net/pipex_local.h
+++ b/sys/net/pipex_local.h
@@ -1,4 +1,4 @@
-/*     $OpenBSD: pipex_local.h,v 1.50 2024/01/23 16:57:53 mvs Exp $    */
+/*     $OpenBSD: pipex_local.h,v 1.51 2024/01/23 17:57:21 mvs Exp $    */
 
 /*
  * Copyright (c) 2009 Internet Initiative Japan Inc.
@@ -156,19 +156,32 @@ struct pipex_l2tp_session {
 
 struct cpumem;
 
+/* special iterator session */
+struct pipex_session_iterator {
+       /* Fields below should be in sync with pipex_session structure */
+       struct radix_node       ps4_rn[2];
+       u_int           flags;                  /* [I] flags, see below */
+       LIST_ENTRY(pipex_session) session_list; /* [L] all session chain */
+};
+
 /* pppac ip-extension session table */
 struct pipex_session {
        struct radix_node       ps4_rn[2];
                                        /* [L] tree glue, and other values */
-
-       struct refcnt pxs_refcnt;
-       struct mutex pxs_mtx;
+       u_int           flags;          /* [I] flags, see below */
+#define PIPEX_SFLAGS_MULTICAST         0x01 /* virtual entry for multicast */
+#define PIPEX_SFLAGS_PPPX              0x02 /* interface is
+                                               point2point(pppx) */
+#define PIPEX_SFLAGS_ITERATOR          0x04 /* iterator session */
 
        LIST_ENTRY(pipex_session) session_list; /* [L] all session chain */
        LIST_ENTRY(pipex_session) state_list;   /* [L] state list chain */
        LIST_ENTRY(pipex_session) id_chain;     /* [L] id hash chain */
        LIST_ENTRY(pipex_session) peer_addr_chain;
                                        /* [L] peer's address hash chain */
+       struct refcnt pxs_refcnt;
+       struct mutex pxs_mtx;
+
        u_int           state;          /* [L] pipex session state */
 #define PIPEX_STATE_INITIAL            0x0000
 #define PIPEX_STATE_OPENED             0x0001
@@ -178,11 +191,6 @@ struct pipex_session {
 
        uint32_t        idle_time;      /* [L] idle time in seconds */
 
-       u_int           flags;          /* [I] flags, see below */
-#define PIPEX_SFLAGS_MULTICAST         0x01 /* virtual entry for multicast */
-#define PIPEX_SFLAGS_PPPX              0x02 /* interface is
-                                               point2point(pppx) */
-
        uint16_t        protocol;               /* [I] tunnel protocol (PK) */
        uint16_t        session_id;             /* [I] session-id (PK) */
        uint16_t        peer_session_id;        /* [I] peer's session-id */
@@ -464,3 +472,5 @@ int                   pipex_ppp_enqueue (struct mbuf *, struct pipex_session *,
 void                  pipex_timer_start (void);
 void                  pipex_timer_stop (void);
 void                  pipex_timer (void *);
+struct pipex_session  *pipex_iterator(struct pipex_session *,
+                          struct pipex_session_iterator *, void *);