From: Alexander Bluhm Subject: Re: raw IP input loop iterator To: Vitaliy Makkoveev Cc: tech@openbsd.org Date: Tue, 5 Nov 2024 15:52:36 +0100 On Tue, Nov 05, 2024 at 05:03:46PM +0300, Vitaliy Makkoveev wrote: > On Tue, Nov 05, 2024 at 01:58:07PM +0100, Alexander Bluhm wrote: > > Hi, > > > > Inspired by mvs@ idea with the iterator in the UDP multicast loop, > > I implemented the same for raw IP input delivery. This removes an > > unneccesary rwlock and only uses the table mutex. > > > > While there, I found some issues with my UDP implementation. When > > comparing the inp address and port, we must hold some lock. So > > assume that iterator already has the table mutex and hold it while > > traversing the list and doing the checks. We are free to release > > the mutex when appending to the the socket buffer and doing the > > upcalls. > > Do we really need this? They could be rebound only once from 0 to > selected source address. I would prefer a clear lock for reading values that another thread can modify. In rip_disconnect() we set inp->inp_faddr.s_addr = INADDR_ANY. As I understand it, soconnect() can call sodisconnect(), so userland can connect and disconnect some socket types arbitrarily. That is the reason why I did put all this under table mutex when I unlocked connect(2). inp_rtableid can be changed by setsockopt(2). Doing a locked comparison gives me a cleaner feeling. Also I think we do less unlock/lock dancing. The common case it to hit one of the continue instructions. Keeping the mutex in this case helps to get through the list quickly. > > I think the goto bad in udp_input does one in_pcbunref(inp) too > > much. If we exited the loop with in_pcb_iterator_abort() inp is > > not NULL, but already unrefed. > > > > I could miss something, but everything is fine with references. You are right, inp is always NULL, there is no bug. I would like to keep the explicit m_freem() and return IPPROTO_DONE anyway. This is what my raw IP code does in the last == NULL case. No need to call in_pcbunref(NULL). bluhm > We follow "last == NULL" branch if no `inp' was found during the > loop. In this case `inp' and `last' are NULL, so in_pcbunref(inp) > is just NULL op. > > If we exited the loop with in_pcb_iterator_abort() `inp' is not > NULL, but `last' is not NULL too, because we assign it to `inp' > just before the check. It holds the reference taken by implicit > "last = in_pcbref(inp)", by the reference taken by iterator was > released by in_pcb_iterator_abort(). The reference taken for > `last' will be released just after udp_sbappend(). > > > In rip_input() move the actual work to rip_sbappend(). This can > > be called without mutex during list traversal and for the final > > element. > > > > ok? > > > > bluhm > > > > Index: kern/kern_sysctl.c > > =================================================================== > > RCS file: /data/mirror/openbsd/cvs/src/sys/kern/kern_sysctl.c,v > > diff -u -p -r1.452 kern_sysctl.c > > --- kern/kern_sysctl.c 5 Nov 2024 10:49:23 -0000 1.452 > > +++ kern/kern_sysctl.c 5 Nov 2024 12:18:15 -0000 > > @@ -1705,8 +1705,11 @@ sysctl_file(int *name, u_int namelen, ch > > mtx_leave(&udb6table.inpt_mtx); > > #endif > > mtx_enter(&rawcbtable.inpt_mtx); > > - TAILQ_FOREACH(inp, &rawcbtable.inpt_queue, inp_queue) > > + TAILQ_FOREACH(inp, &rawcbtable.inpt_queue, inp_queue) { > > + if (in_pcb_is_iterator(inp)) > > + continue; > > FILLSO(inp->inp_socket); > > + } > > mtx_leave(&rawcbtable.inpt_mtx); > > #ifdef INET6 > > mtx_enter(&rawin6pcbtable.inpt_mtx); > > Index: netinet/in_pcb.c > > =================================================================== > > RCS file: /data/mirror/openbsd/cvs/src/sys/netinet/in_pcb.c,v > > diff -u -p -r1.304 in_pcb.c > > --- netinet/in_pcb.c 5 Nov 2024 10:49:23 -0000 1.304 > > +++ netinet/in_pcb.c 5 Nov 2024 12:18:15 -0000 > > @@ -650,7 +650,7 @@ in_pcb_iterator(struct inpcbtable *table > > { > > struct inpcb *tmp; > > > > - mtx_enter(&table->inpt_mtx); > > + MUTEX_ASSERT_LOCKED(&table->inpt_mtx); > > > > if (inp) > > tmp = TAILQ_NEXT((struct inpcb *)iter, inp_queue); > > @@ -663,6 +663,7 @@ in_pcb_iterator(struct inpcbtable *table > > if (inp) { > > TAILQ_REMOVE(&table->inpt_queue, (struct inpcb *)iter, > > inp_queue); > > + in_pcbunref(inp); > > } > > if (tmp) { > > TAILQ_INSERT_AFTER(&table->inpt_queue, tmp, > > @@ -670,10 +671,6 @@ in_pcb_iterator(struct inpcbtable *table > > in_pcbref(tmp); > > } > > > > - mtx_leave(&table->inpt_mtx); > > - > > - in_pcbunref(inp); > > - > > return tmp; > > } > > > > @@ -681,16 +678,13 @@ void > > in_pcb_iterator_abort(struct inpcbtable *table, struct inpcb *inp, > > struct inpcb_iterator *iter) > > { > > - mtx_enter(&table->inpt_mtx); > > + MUTEX_ASSERT_LOCKED(&table->inpt_mtx); > > > > if (inp) { > > TAILQ_REMOVE(&table->inpt_queue, (struct inpcb *)iter, > > inp_queue); > > + in_pcbunref(inp); > > } > > - > > - mtx_leave(&table->inpt_mtx); > > - > > - in_pcbunref(inp); > > } > > > > void > > Index: netinet/raw_ip.c > > =================================================================== > > RCS file: /data/mirror/openbsd/cvs/src/sys/netinet/raw_ip.c,v > > diff -u -p -r1.160 raw_ip.c > > --- netinet/raw_ip.c 12 Jul 2024 19:50:35 -0000 1.160 > > +++ netinet/raw_ip.c 5 Nov 2024 12:18:15 -0000 > > @@ -116,6 +116,9 @@ const struct pr_usrreqs rip_usrreqs = { > > .pru_peeraddr = in_peeraddr, > > }; > > > > +void rip_sbappend(struct inpcb *, struct mbuf *, struct ip *, > > + struct sockaddr_in *); > > + > > /* > > * Initialize raw connection block q. > > */ > > @@ -130,8 +133,8 @@ rip_input(struct mbuf **mp, int *offp, i > > { > > struct mbuf *m = *mp; > > struct ip *ip = mtod(m, struct ip *); > > - struct inpcb *inp; > > - SIMPLEQ_HEAD(, inpcb) inpcblist; > > + struct inpcb_iterator iter = { .inp_table = NULL }; > > + struct inpcb *inp, *last; > > struct in_addr *key; > > struct counters_ref ref; > > uint64_t *counters; > > @@ -163,10 +166,9 @@ rip_input(struct mbuf **mp, int *offp, i > > } > > } > > #endif > > - SIMPLEQ_INIT(&inpcblist); > > - rw_enter_write(&rawcbtable.inpt_notify); > > mtx_enter(&rawcbtable.inpt_mtx); > > - TAILQ_FOREACH(inp, &rawcbtable.inpt_queue, inp_queue) { > > + last = inp = NULL; > > + while ((inp = in_pcb_iterator(&rawcbtable, inp, &iter)) != NULL) { > > KASSERT(!ISSET(inp->inp_flags, INP_IPV6)); > > > > /* > > @@ -190,14 +192,23 @@ rip_input(struct mbuf **mp, int *offp, i > > inp->inp_faddr.s_addr != ip->ip_src.s_addr) > > continue; > > > > - in_pcbref(inp); > > - SIMPLEQ_INSERT_TAIL(&inpcblist, inp, inp_notify); > > + if (last != NULL) { > > + struct mbuf *n; > > + > > + mtx_leave(&rawcbtable.inpt_mtx); > > + > > + n = m_copym(m, 0, M_COPYALL, M_NOWAIT); > > + if (n != NULL) > > + rip_sbappend(last, n, ip, &ripsrc); > > + in_pcbunref(last); > > + > > + mtx_enter(&rawcbtable.inpt_mtx); > > + } > > + last = in_pcbref(inp); > > } > > mtx_leave(&rawcbtable.inpt_mtx); > > > > - if (SIMPLEQ_EMPTY(&inpcblist)) { > > - rw_exit_write(&rawcbtable.inpt_notify); > > - > > + if (last == NULL) { > > if (ip->ip_p != IPPROTO_ICMP) > > icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_PROTOCOL, > > 0, 0); > > @@ -212,42 +223,34 @@ rip_input(struct mbuf **mp, int *offp, i > > return IPPROTO_DONE; > > } > > > > - while ((inp = SIMPLEQ_FIRST(&inpcblist)) != NULL) { > > - struct mbuf *n, *opts = NULL; > > - > > - SIMPLEQ_REMOVE_HEAD(&inpcblist, inp_notify); > > - if (SIMPLEQ_EMPTY(&inpcblist)) > > - n = m; > > - else > > - n = m_copym(m, 0, M_COPYALL, M_NOWAIT); > > - if (n != NULL) { > > - struct socket *so = inp->inp_socket; > > - int ret = 0; > > - > > - if (inp->inp_flags & INP_CONTROLOPTS || > > - so->so_options & SO_TIMESTAMP) > > - ip_savecontrol(inp, &opts, ip, n); > > - > > - mtx_enter(&so->so_rcv.sb_mtx); > > - if (!ISSET(inp->inp_socket->so_rcv.sb_state, > > - SS_CANTRCVMORE)) { > > - ret = sbappendaddr(so, &so->so_rcv, > > - sintosa(&ripsrc), n, opts); > > - } > > - mtx_leave(&so->so_rcv.sb_mtx); > > - > > - if (ret == 0) { > > - m_freem(n); > > - m_freem(opts); > > - ipstat_inc(ips_noproto); > > - } else > > - sorwakeup(so); > > - } > > - in_pcbunref(inp); > > - } > > - rw_exit_write(&rawcbtable.inpt_notify); > > + rip_sbappend(last, m, ip, &ripsrc); > > + in_pcbunref(last); > > > > return IPPROTO_DONE; > > +} > > + > > +void > > +rip_sbappend(struct inpcb *inp, struct mbuf *m, struct ip *ip, > > + struct sockaddr_in *ripsrc) > > +{ > > + struct socket *so = inp->inp_socket; > > + struct mbuf *opts = NULL; > > + int ret = 0; > > + > > + if (inp->inp_flags & INP_CONTROLOPTS || so->so_options & SO_TIMESTAMP) > > + ip_savecontrol(inp, &opts, ip, m); > > + > > + mtx_enter(&so->so_rcv.sb_mtx); > > + if (!ISSET(inp->inp_socket->so_rcv.sb_state, SS_CANTRCVMORE)) > > + ret = sbappendaddr(so, &so->so_rcv, sintosa(ripsrc), m, opts); > > + mtx_leave(&so->so_rcv.sb_mtx); > > + > > + if (ret == 0) { > > + m_freem(m); > > + m_freem(opts); > > + ipstat_inc(ips_noproto); > > + } else > > + sorwakeup(so); > > } > > > > /* > > Index: netinet/udp_usrreq.c > > =================================================================== > > RCS file: /data/mirror/openbsd/cvs/src/sys/netinet/udp_usrreq.c,v > > diff -u -p -r1.326 udp_usrreq.c > > --- netinet/udp_usrreq.c 5 Nov 2024 10:49:23 -0000 1.326 > > +++ netinet/udp_usrreq.c 5 Nov 2024 12:18:15 -0000 > > @@ -409,6 +409,7 @@ udp_input(struct mbuf **mp, int *offp, i > > #endif > > table = &udbtable; > > > > + mtx_enter(&table->inpt_mtx); > > last = inp = NULL; > > while ((inp = in_pcb_iterator(table, inp, &iter)) != NULL) { > > if (ip6) > > @@ -464,12 +465,16 @@ udp_input(struct mbuf **mp, int *offp, i > > if (last != NULL) { > > struct mbuf *n; > > > > + mtx_leave(&table->inpt_mtx); > > + > > n = m_copym(m, 0, M_COPYALL, M_NOWAIT); > > if (n != NULL) { > > udp_sbappend(last, n, ip, ip6, iphlen, > > uh, &srcsa.sa, 0); > > } > > in_pcbunref(last); > > + > > + mtx_enter(&table->inpt_mtx); > > } > > last = in_pcbref(inp); > > > > @@ -487,6 +492,7 @@ udp_input(struct mbuf **mp, int *offp, i > > break; > > } > > } > > + mtx_leave(&table->inpt_mtx); > > > > if (last == NULL) { > > /* > > @@ -495,7 +501,8 @@ udp_input(struct mbuf **mp, int *offp, i > > * for a broadcast or multicast datgram.) > > */ > > udpstat_inc(udps_noportbcast); > > - goto bad; > > + m_freem(m); > > + return IPPROTO_DONE; > > } > > > > udp_sbappend(last, m, ip, ip6, iphlen, uh, &srcsa.sa, 0); > >