Date: Thu, 17 Oct 2019 21:33:01 +0000 (UTC) From: Conrad Meyer <cem@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r353700 - in head: share/man/man4 sys/amd64/conf sys/conf sys/gdb sys/i386/conf sys/kern sys/net sys/sys Message-ID: <201910172133.x9HLX1kl071044@repo.freebsd.org>
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Author: cem Date: Thu Oct 17 21:33:01 2019 New Revision: 353700 URL: https://svnweb.freebsd.org/changeset/base/353700 Log: Implement NetGDB(4) NetGDB(4) is a component of a system using a panic-time network stack to remotely debug crashed FreeBSD kernels over the network, instead of traditional serial interfaces. There are three pieces in the complete NetGDB system. First, a dedicated proxy server must be running to accept connections from both NetGDB and gdb(1), and pass bidirectional traffic between the two protocols. Second, the NetGDB client is activated much like ordinary 'gdb' and similarly to 'netdump' in ddb(4) after a panic. Like other debugnet(4) clients (netdump(4)), the network interface on the route to the proxy server must be online and support debugnet(4). Finally, the remote (k)gdb(1) uses 'target remote <proxy>:<port>' (like any other TCP remote) to connect to the proxy server. The NetGDB v1 protocol speaks the literal GDB remote serial protocol, and uses a 1:1 relationship between GDB packets and sequences of debugnet packets (fragmented by MTU). There is no encryption utilized to keep debugging sessions private, so this is only appropriate for local segments or trusted networks. Submitted by: John Reimer <john.reimer AT emc.com> (earlier version) Discussed some with: emaste, markj Relnotes: sure Differential Revision: https://reviews.freebsd.org/D21568 Added: head/share/man/man4/netgdb.4 (contents, props changed) head/sys/gdb/netgdb.c (contents, props changed) head/sys/gdb/netgdb.h (contents, props changed) Modified: head/share/man/man4/Makefile head/share/man/man4/ddb.4 head/sys/amd64/conf/GENERIC head/sys/conf/NOTES head/sys/conf/files head/sys/conf/options head/sys/gdb/gdb.h head/sys/gdb/gdb_int.h head/sys/gdb/gdb_main.c head/sys/gdb/gdb_packet.c head/sys/i386/conf/GENERIC head/sys/kern/subr_kdb.c head/sys/net/debugnet.c head/sys/net/debugnet.h head/sys/net/debugnet_inet.c head/sys/net/debugnet_int.h head/sys/sys/kdb.h head/sys/sys/param.h Modified: head/share/man/man4/Makefile ============================================================================== --- head/share/man/man4/Makefile Thu Oct 17 21:25:50 2019 (r353699) +++ head/share/man/man4/Makefile Thu Oct 17 21:33:01 2019 (r353700) @@ -307,6 +307,7 @@ MAN= aac.4 \ net80211.4 \ netdump.4 \ netfpga10g_nf10bmac.4 \ + netgdb.4 \ netgraph.4 \ netintro.4 \ netmap.4 \ Modified: head/share/man/man4/ddb.4 ============================================================================== --- head/share/man/man4/ddb.4 Thu Oct 17 21:25:50 2019 (r353699) +++ head/share/man/man4/ddb.4 Thu Oct 17 21:33:01 2019 (r353700) @@ -1211,6 +1211,15 @@ Finally, the .Ic netdump command does not provide any way to configure compression or encryption. .Pp +.It Ic netgdb Fl s Ar server Oo Fl g Ar gateway Fl c Ar client Fl i Ar iface Oc +Initiate a +.Xr netgdb 4 +session with the provided parameters. +.Pp +.Ic netgdb +has identical limitations to +.Ic netdump . +.Pp .It Ic capture on .It Ic capture off .It Ic capture reset Added: head/share/man/man4/netgdb.4 ============================================================================== --- /dev/null 00:00:00 1970 (empty, because file is newly added) +++ head/share/man/man4/netgdb.4 Thu Oct 17 21:33:01 2019 (r353700) @@ -0,0 +1,147 @@ +.\"- +.\" Copyright (c) 2019 Conrad Meyer <cem@FreeBSD.org> +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND +.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE +.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL +.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS +.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) +.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY +.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +.\" SUCH DAMAGE. +.\" +.\" $FreeBSD$ +.\" +.Dd October 17, 2019 +.Dt NETGDB 4 +.Os +.Sh NAME +.Nm netgdb +.Nd protocol for debugging the kernel with GDB over the network +.Sh SYNOPSIS +NetGDB support is compiled by default, if DDB, GDB, and INET are enabled. +To build a kernel without it, add the following line to your kernel +configuration file: +.Bd -ragged -offset indent +.Cd "nooptions NETGDB" +.Ed +.Sh DESCRIPTION +.Nm +is a UDP-based protocol for communicating with a remote GDB client via an +intermediary proxy. +.Pp +A +.Nm +session is started by using the +.Ic netgdb Fl s Ar server Oo Fl g Ar gateway Fl c Ar client Fl i Ar iface Oc +command in +.Xr ddb 4 +to connect to a proxy server. +When the connection is made, the proxy server logs a message that a +.Nm +client has connected. +It subsequently establishes a TCP listening socket and logs a message +specifying which port it is listening on. +Then it waits for a GDB client to connect. +The GDB command to connect is: +.Bd -ragged -offset indent +.Ic target remote Aq Ar proxyip:proxyport +.Ed +.Pp +At this point, the server proxies traffic back and forth between +.Nm +and the ordinary GDB client, speaking the ordinary GDB remote protocol. +The +.Nm +session is identical to any other kernel GDB sesssion from the perspective +of the GDB debugger. +.Sh IMPLEMENTATION NOTES +The UDP protocol is based on the same packet structure and a subset of the +exact same message types as +.Xr netdump 4 . +It uses the +.Dv HERALD , +.Dv DATA ( née VMCORE ) , +and +.Dv FINISHED +message types. +Like +.Xr netdump 4 , +the client's initial +.Dv HERALD +message is acknowledged from a random source port, and the client sends +subsequent communication to that port. +.Pp +Unlike +.Xr netdump 4 , +the initial +.Dv HERALD +port is 20025. +Additionally, +the proxy server sends responses to the source port of the client's initial +.Dv HERALD , +rather than a separate reserved port. +.Nm +message and acknowledgements are bidirectional. +The sequence number and acknowledgement protocol is otherwise identical to +the unidirectional version used by netdump; it just runs in both directions. +Acknowledgements are sent to and from the same addresses and ports as +regular messages. +.Pp +The first version of the +.Nm +protocol uses the protocol number +.Dv Sq 0x2515f095 +in the 32-bit +.Va aux2 +parameter of the initial +.Dv HERALD +message. +.Pp +The list of supported network drivers and protocol families is identical to +that of +.Xr netdump 4 . +.Sh DIAGNOSTICS +The following variable is available via both +.Xr sysctl 8 +and +.Xr loader 8 +(as a tunable): +.Bl -tag -width "indent" +.It Va debug.gdb.netgdb.debug +Control debug message verbosity. +Debug messages are disabled by default. +They may be enabled by setting the variable to a non-zero value. +.El +.Sh SEE ALSO +.Xr ddb 4 , +.Xr gdb 4 , +.Xr netdump 4 +.Sh HISTORY +.Nm +first appeared in +.Fx 13.0 . +.Sh BUGS +.Nm +may only be used after the kernel has panicked, due to limitations in the +treatment of locking primitives under +.Xr ddb 4 . +.Sh SECURITY CONSIDERATIONS +Version 1 of the +.Nm +protocol has no security properties whatsoever. +All messages are sent and acknowledged in cleartext, and no message +authentication codes are used to prevent attackers from forging messages. +It is absolutely inappropriate for use across the public internet. Modified: head/sys/amd64/conf/GENERIC ============================================================================== --- head/sys/amd64/conf/GENERIC Thu Oct 17 21:25:50 2019 (r353699) +++ head/sys/amd64/conf/GENERIC Thu Oct 17 21:33:01 2019 (r353700) @@ -113,6 +113,7 @@ options GZIO # gzip-compressed kernel and user dump options ZSTDIO # zstd-compressed kernel and user dumps options DEBUGNET # debugnet networking options NETDUMP # netdump(4) client support +options NETGDB # netgdb(4) client support # Make an SMP-capable kernel by default options SMP # Symmetric MultiProcessor Kernel Modified: head/sys/conf/NOTES ============================================================================== --- head/sys/conf/NOTES Thu Oct 17 21:25:50 2019 (r353699) +++ head/sys/conf/NOTES Thu Oct 17 21:33:01 2019 (r353700) @@ -1038,13 +1038,17 @@ options TCP_SIGNATURE #include support for RFC 2385 # a smooth scheduling of the traffic. options DUMMYNET +# The DEBUGNET option enables a basic debug/panic-time networking API. It +# is used by NETDUMP and NETGDB. +options DEBUGNET + # The NETDUMP option enables netdump(4) client support in the kernel. # This allows a panicking kernel to transmit a kernel dump to a remote host. options NETDUMP -# The DEBUGNET option enables a basic debug/panic-time networking API. It -# is used by NETDUMP. -options DEBUGNET +# The NETGDB option enables netgdb(4) support in the kernel. This allows a +# panicking kernel to be debugged as a GDB remote over the network. +options NETGDB ##################################################################### # FILESYSTEM OPTIONS Modified: head/sys/conf/files ============================================================================== --- head/sys/conf/files Thu Oct 17 21:25:50 2019 (r353699) +++ head/sys/conf/files Thu Oct 17 21:33:01 2019 (r353700) @@ -3546,6 +3546,7 @@ fs/tmpfs/tmpfs_subr.c optional tmpfs gdb/gdb_cons.c optional gdb gdb/gdb_main.c optional gdb gdb/gdb_packet.c optional gdb +gdb/netgdb.c optional ddb debugnet gdb netgdb inet geom/bde/g_bde.c optional geom_bde geom/bde/g_bde_crypt.c optional geom_bde geom/bde/g_bde_lock.c optional geom_bde Modified: head/sys/conf/options ============================================================================== --- head/sys/conf/options Thu Oct 17 21:25:50 2019 (r353699) +++ head/sys/conf/options Thu Oct 17 21:33:01 2019 (r353700) @@ -319,10 +319,12 @@ NFS_ROOT opt_nfsroot.h # SMB/CIFS requester NETSMB opt_netsmb.h -# Enable netdump(4) client support. -NETDUMP opt_global.h # Enable debugnet(4) networking support. DEBUGNET opt_global.h +# Enable netdump(4) client support. +NETDUMP opt_global.h +# Enable netgdb(4) support. +NETGDB opt_global.h # Options used only in subr_param.c. HZ opt_param.h Modified: head/sys/gdb/gdb.h ============================================================================== --- head/sys/gdb/gdb.h Thu Oct 17 21:25:50 2019 (r353699) +++ head/sys/gdb/gdb.h Thu Oct 17 21:33:01 2019 (r353700) @@ -46,7 +46,15 @@ struct gdb_dbgport { gdb_putc_f *gdb_putc; gdb_term_f *gdb_term; int gdb_active; + void (*gdb_sendpacket)(const void *, size_t); + int gdb_dbfeatures; }; + +#define GDB_DBGP_FEAT_WANTTERM 0x1 /* Want gdb_term() invocation when + leaving GDB. gdb_term has been + deadcode and never invoked for so + long I don't want to just blindly + start invoking it without opt-in. */ #define GDB_DBGPORT(name, probe, init, term, getc, putc) \ static struct gdb_dbgport name##_gdb_dbgport = { \ Modified: head/sys/gdb/gdb_int.h ============================================================================== --- head/sys/gdb/gdb_int.h Thu Oct 17 21:25:50 2019 (r353699) +++ head/sys/gdb/gdb_int.h Thu Oct 17 21:33:01 2019 (r353700) @@ -31,8 +31,14 @@ #ifndef _GDB_GDB_INT_H_ #define _GDB_GDB_INT_H_ +#include "opt_ddb.h" + #include <sys/sysctl.h> +#ifdef DDB +#include <ddb/ddb.h> +#endif + #ifndef EOF #define EOF (-1) #endif @@ -47,6 +53,11 @@ void gdb_consinit(void); extern char *gdb_rxp; extern size_t gdb_rxsz; extern char *gdb_txp; + +#ifdef DDB +/* If set, return to DDB when controlling GDB detaches. */ +extern bool gdb_return_to_ddb; +#endif int gdb_rx_begin(void); int gdb_rx_equal(const char *); Modified: head/sys/gdb/gdb_main.c ============================================================================== --- head/sys/gdb/gdb_main.c Thu Oct 17 21:25:50 2019 (r353699) +++ head/sys/gdb/gdb_main.c Thu Oct 17 21:33:01 2019 (r353700) @@ -60,6 +60,10 @@ int gdb_listening = 0; static unsigned char gdb_bindata[64]; +#ifdef DDB +bool gdb_return_to_ddb = false; +#endif + static int gdb_init(void) { @@ -569,6 +573,26 @@ unrecognized: return; } +static void +gdb_handle_detach(void) +{ + kdb_cpu_clear_singlestep(); + gdb_listening = 0; + + if (gdb_cur->gdb_dbfeatures & GDB_DBGP_FEAT_WANTTERM) + gdb_cur->gdb_term(); + +#ifdef DDB + if (!gdb_return_to_ddb) + return; + + gdb_return_to_ddb = false; + + if (kdb_dbbe_select("ddb") != 0) + printf("The ddb backend could not be selected.\n"); +#endif +} + static int gdb_trap(int type, int code) { @@ -638,7 +662,7 @@ gdb_trap(int type, int code) } case 'D': { /* Detach */ gdb_tx_ok(); - kdb_cpu_clear_singlestep(); + gdb_handle_detach(); return (1); } case 'g': { /* Read registers. */ @@ -675,8 +699,7 @@ gdb_trap(int type, int code) break; } case 'k': /* Kill request. */ - kdb_cpu_clear_singlestep(); - gdb_listening = 1; + gdb_handle_detach(); return (1); case 'm': { /* Read memory. */ uintmax_t addr, size; Modified: head/sys/gdb/gdb_packet.c ============================================================================== --- head/sys/gdb/gdb_packet.c Thu Oct 17 21:25:50 2019 (r353699) +++ head/sys/gdb/gdb_packet.c Thu Oct 17 21:33:01 2019 (r353700) @@ -45,7 +45,27 @@ __FBSDID("$FreeBSD$"); static char gdb_rxbuf[GDB_BUFSZ]; char *gdb_rxp = NULL; size_t gdb_rxsz = 0; -static char gdb_txbuf[GDB_BUFSZ]; + +/* + * The goal here is to allow in-place framing without making the math around + * 'gdb_txbuf' more complicated. A generous reading of union special rule for + * "common initial sequence" suggests this may be valid in standard C99 and + * later. + */ +static union { + struct _midbuf { + char mb_pad1; + char mb_buf[GDB_BUFSZ]; + char mb_pad2[4]; + } __packed txu_midbuf; + /* sizeof includes trailing nul byte and this is intentional. */ + char txu_fullbuf[GDB_BUFSZ + sizeof("$#..")]; +} gdb_tx_u; +#define gdb_txbuf gdb_tx_u.txu_midbuf.mb_buf +#define gdb_tx_fullbuf gdb_tx_u.txu_fullbuf +_Static_assert(sizeof(gdb_tx_u.txu_midbuf) == sizeof(gdb_tx_u.txu_fullbuf) && + offsetof(struct _midbuf, mb_buf) == 1, + "assertions necessary for correctness"); char *gdb_txp = NULL; /* Used in inline functions. */ #define C2N(c) (((c) < 'A') ? (c) - '0' : \ @@ -68,6 +88,9 @@ gdb_getc(void) if (c == CTRL('C')) { printf("Received ^C; trying to switch back to ddb.\n"); + if (gdb_cur->gdb_dbfeatures & GDB_DBGP_FEAT_WANTTERM) + gdb_cur->gdb_term(); + if (kdb_dbbe_select("ddb") != 0) printf("The ddb backend could not be selected.\n"); else { @@ -218,6 +241,29 @@ gdb_tx_begin(char tp) gdb_tx_char(tp); } +/* + * Take raw packet buffer and perform typical GDB packet framing, but not run- + * length encoding, before forwarding to driver ::gdb_sendpacket() routine. + */ +static void +gdb_tx_sendpacket(void) +{ + size_t msglen, i; + unsigned char csum; + + msglen = gdb_txp - gdb_txbuf; + + /* Add GDB packet framing */ + gdb_tx_fullbuf[0] = '$'; + + csum = 0; + for (i = 0; i < msglen; i++) + csum += (unsigned char)gdb_txbuf[i]; + snprintf(&gdb_tx_fullbuf[1 + msglen], 4, "#%02x", (unsigned)csum); + + gdb_cur->gdb_sendpacket(gdb_tx_fullbuf, msglen + 4); +} + int gdb_tx_end(void) { @@ -226,6 +272,11 @@ gdb_tx_end(void) unsigned char c, cksum; do { + if (gdb_cur->gdb_sendpacket != NULL) { + gdb_tx_sendpacket(); + goto getack; + } + gdb_cur->gdb_putc('$'); cksum = 0; @@ -284,6 +335,7 @@ gdb_tx_end(void) c = cksum & 0x0f; gdb_cur->gdb_putc(N2C(c)); +getack: c = gdb_getc(); } while (c != '+'); Added: head/sys/gdb/netgdb.c ============================================================================== --- /dev/null 00:00:00 1970 (empty, because file is newly added) +++ head/sys/gdb/netgdb.c Thu Oct 17 21:33:01 2019 (r353700) @@ -0,0 +1,406 @@ +/*- + * SPDX-License-Identifier: BSD-2-Clause-FreeBSD + * + * Copyright (c) 2019 Isilon Systems, LLC. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + */ + +/* + * netgdb.c + * FreeBSD subsystem supporting debugging the FreeBSD kernel over the network. + * + * There are three pieces necessary to use NetGDB. + * + * First, a dedicated proxy server must be running to accept connections from + * both NetGDB and gdb(1), and pass bidirectional traffic between the two + * protocols. + * + * Second, The NetGDB client is activated much like ordinary 'gdb' and + * similarly to 'netdump' in ddb(4). Like other debugnet(4) clients + * (netdump(4)), the network interface on the route to the proxy server must be + * online and support debugnet(4). + * + * Finally, the remote (k)gdb(1) uses 'target remote <proxy>:<port>' to connect + * to the proxy server. + * + * NetGDBv1 speaks the literal GDB remote serial protocol, and uses a 1:1 + * relationship between GDB packets and plain debugnet packets. There is no + * encryption utilized to keep debugging sessions private, so this is only + * appropriate for local segments or trusted networks. + */ + +#include <sys/cdefs.h> +__FBSDID("$FreeBSD$"); + +#include "opt_ddb.h" +#ifndef DDB +#error "NetGDB cannot be used without DDB at this time" +#endif + +#include <sys/param.h> +#include <sys/kdb.h> +#include <sys/sbuf.h> +#include <sys/socket.h> +#include <sys/sysctl.h> +#include <sys/ttydefaults.h> + +#include <machine/gdb_machdep.h> + +#ifdef DDB +#include <ddb/ddb.h> +#include <ddb/db_command.h> +#include <ddb/db_lex.h> +#endif + +#include <net/debugnet.h> +#include <net/if.h> +#include <net/if_var.h> +#include <net/route.h> + +#include <gdb/gdb.h> +#include <gdb/gdb_int.h> +#include <gdb/netgdb.h> + +FEATURE(netgdb, "NetGDB support"); +SYSCTL_NODE(_debug_gdb, OID_AUTO, netgdb, CTLFLAG_RD, NULL, + "NetGDB parameters"); + +static unsigned netgdb_debug; +SYSCTL_UINT(_debug_gdb_netgdb, OID_AUTO, debug, CTLFLAG_RWTUN, + &netgdb_debug, 0, + "Debug message verbosity (0: off; 1: on)"); + +#define NETGDB_DEBUG(f, ...) do { \ + if (netgdb_debug > 0) \ + printf(("%s [%s:%d]: " f), __func__, __FILE__, __LINE__, ## \ + __VA_ARGS__); \ +} while (false) + +static void netgdb_fini(void); + +/* Runtime state. */ +static char netgdb_rxbuf[GDB_BUFSZ + 16]; /* Some overhead for framing. */ +static struct sbuf netgdb_rxsb; +static ssize_t netgdb_rx_off; + +static struct debugnet_pcb *netgdb_conn; +static struct gdb_dbgport *netgdb_prev_dbgport; +static int *netgdb_prev_kdb_inactive; + +/* TODO(CEM) disable ack mode */ + +/* + * Receive non-TX ACK packets on the client port. + * + * The mbuf chain will have all non-debugnet framing headers removed + * (ethernet, inet, udp). It will start with a debugnet_msg_hdr, of + * which the header is guaranteed to be contiguous. If m_pullup is + * used, the supplied in-out mbuf pointer should be updated + * appropriately. + * + * If the handler frees the mbuf chain, it should set the mbuf pointer + * to NULL. Otherwise, the debugnet input framework will free the + * chain. + */ +static void +netgdb_rx(struct debugnet_pcb *pcb, struct mbuf **mb) +{ + const struct debugnet_msg_hdr *dnh; + struct mbuf *m; + uint32_t rlen, count; + int error; + + m = *mb; + dnh = mtod(m, const void *); + + if (ntohl(dnh->mh_type) == DEBUGNET_FINISHED) { + sbuf_putc(&netgdb_rxsb, CTRL('C')); + return; + } + + if (ntohl(dnh->mh_type) != DEBUGNET_DATA) { + printf("%s: Got unexpected debugnet message %u\n", + __func__, ntohl(dnh->mh_type)); + return; + } + + rlen = ntohl(dnh->mh_len); +#define _SBUF_FREESPACE(s) ((s)->s_size - ((s)->s_len + 1)) + if (_SBUF_FREESPACE(&netgdb_rxsb) < rlen) { + NETGDB_DEBUG("Backpressure: Not ACKing RX of packet that " + "would overflow our buffer (%zd/%zd used).\n", + netgdb_rxsb.s_len, netgdb_rxsb.s_size); + return; + } +#undef _SBUF_FREESPACE + + error = debugnet_ack_output(pcb, dnh->mh_seqno); + if (error != 0) { + printf("%s: Couldn't ACK rx packet %u; %d\n", __func__, + ntohl(dnh->mh_seqno), error); + /* + * Sender will re-xmit, and assuming the condition is + * transient, we'll process the packet's contentss later. + */ + return; + } + + m_adj(m, sizeof(*dnh)); + dnh = NULL; + + /* + * Inlined m_apply -- why isn't there a macro or inline function + * version? + */ + while (m != NULL && m->m_len == 0) + m = m->m_next; + while (rlen > 0) { + MPASS(m != NULL && m->m_len >= 0); + count = min((uint32_t)m->m_len, rlen); + (void)sbuf_bcat(&netgdb_rxsb, mtod(m, const void *), count); + rlen -= count; + m = m->m_next; + } +} + +/* + * The following routines implement a pseudo GDB debugport (an emulated serial + * driver that the MI gdb(4) code does I/O with). + */ + +static int +netgdb_dbg_getc(void) +{ + int c; + + while (true) { + /* Pull bytes off any currently cached packet first. */ + if (netgdb_rx_off < sbuf_len(&netgdb_rxsb)) { + c = netgdb_rxsb.s_buf[netgdb_rx_off]; + netgdb_rx_off++; + break; + } + + /* Reached EOF? Reuse buffer. */ + sbuf_clear(&netgdb_rxsb); + netgdb_rx_off = 0; + + /* Check for CTRL-C on console/serial, if any. */ + if (netgdb_prev_dbgport != NULL) { + c = netgdb_prev_dbgport->gdb_getc(); + if (c == CTRL('C')) + break; + } + + debugnet_network_poll(netgdb_conn); + } + + if (c == CTRL('C')) { + netgdb_fini(); + /* Caller gdb_getc() will print that we got ^C. */ + } + return (c); +} + +static void +netgdb_dbg_sendpacket(const void *buf, size_t len) +{ + struct debugnet_proto_aux aux; + int error; + + MPASS(len <= UINT32_MAX); + + /* + * GDB packet boundaries matter. debugnet_send() fragments a single + * request into many sequential debugnet messages. Mark full packet + * length and offset for potential reassembly by the proxy. + */ + aux = (struct debugnet_proto_aux) { + .dp_aux2 = len, + }; + + error = debugnet_send(netgdb_conn, DEBUGNET_DATA, buf, len, &aux); + if (error != 0) { + printf("%s: Network error: %d; trying to switch back to ddb.\n", + __func__, error); + netgdb_fini(); + + if (kdb_dbbe_select("ddb") != 0) + printf("The ddb backend could not be selected.\n"); + else { + printf("using longjmp, hope it works!\n"); + kdb_reenter(); + } + } + +} + +/* Just used for + / - GDB-level ACKs. */ +static void +netgdb_dbg_putc(int i) +{ + char c; + + c = i; + netgdb_dbg_sendpacket(&c, 1); + +} + +static struct gdb_dbgport netgdb_gdb_dbgport = { + .gdb_name = "netgdb", + .gdb_getc = netgdb_dbg_getc, + .gdb_putc = netgdb_dbg_putc, + .gdb_term = netgdb_fini, + .gdb_sendpacket = netgdb_dbg_sendpacket, + .gdb_dbfeatures = GDB_DBGP_FEAT_WANTTERM, +}; + +static void +netgdb_init(void) +{ + struct kdb_dbbe *be, **iter; + + /* + * Force enable GDB. (If no other debugports were registered at boot, + * KDB thinks it doesn't exist.) + */ + SET_FOREACH(iter, kdb_dbbe_set) { + be = *iter; + if (strcmp(be->dbbe_name, "gdb") != 0) + continue; + if (be->dbbe_active == -1) { + netgdb_prev_kdb_inactive = &be->dbbe_active; + be->dbbe_active = 0; + } + break; + } + + /* Force netgdb debugport. */ + netgdb_prev_dbgport = gdb_cur; + gdb_cur = &netgdb_gdb_dbgport; + + sbuf_new(&netgdb_rxsb, netgdb_rxbuf, sizeof(netgdb_rxbuf), + SBUF_FIXEDLEN); + netgdb_rx_off = 0; +} + +static void +netgdb_fini(void) +{ + + /* TODO: tear down conn gracefully? */ + if (netgdb_conn != NULL) { + debugnet_free(netgdb_conn); + netgdb_conn = NULL; + } + + sbuf_delete(&netgdb_rxsb); + + gdb_cur = netgdb_prev_dbgport; + + if (netgdb_prev_kdb_inactive != NULL) { + *netgdb_prev_kdb_inactive = -1; + netgdb_prev_kdb_inactive = NULL; + } +} + +#ifdef DDB +/* + * Usage: netgdb -s <server> [-g <gateway -c <localip> -i <interface>] + * + * Order is not significant. + * + * Currently, this command does not support configuring encryption or + * compression. + */ +DB_FUNC(netgdb, db_netgdb_cmd, db_cmd_table, CS_OWN, NULL) +{ + struct debugnet_ddb_config params; + struct debugnet_conn_params dcp; + struct debugnet_pcb *pcb; + int error; + + if (panicstr == NULL) { + /* TODO: This limitation should be removed in future work. */ + printf("%s: netgdb is currently limited to use only after a " + "panic. Sorry.\n", __func__); + return; + } + + error = debugnet_parse_ddb_cmd("netgdb", ¶ms); + if (error != 0) { + db_printf("Error configuring netgdb: %d\n", error); + return; + } + + /* + * Must initialize netgdb_rxsb before debugnet_connect(), because we + * might be getting rx handler callbacks from the send->poll path + * during debugnet_connect(). + */ + netgdb_init(); + + if (!params.dd_has_client) + params.dd_client = INADDR_ANY; + if (!params.dd_has_gateway) + params.dd_gateway = INADDR_ANY; + + dcp = (struct debugnet_conn_params) { + .dc_ifp = params.dd_ifp, + .dc_client = params.dd_client, + .dc_server = params.dd_server, + .dc_gateway = params.dd_gateway, + .dc_herald_port = NETGDB_HERALDPORT, + .dc_client_port = NETGDB_CLIENTPORT, + .dc_herald_aux2 = NETGDB_PROTO_V1, + .dc_rx_handler = netgdb_rx, + }; + + error = debugnet_connect(&dcp, &pcb); + if (error != 0) { + printf("failed to contact netgdb server: %d\n", error); + netgdb_fini(); + return; + } + + netgdb_conn = pcb; + + if (kdb_dbbe_select("gdb") != 0) { + db_printf("The remote GDB backend could not be selected.\n"); + netgdb_fini(); + return; + } + + /* + * Mark that we are done in ddb(4). Return -> kdb_trap() should + * re-enter with the new backend. + */ + db_cmd_loop_done = 1; + gdb_return_to_ddb = true; + db_printf("(detaching GDB will return control to DDB)\n"); +#if 0 + /* Aspirational, but does not work reliably. */ + db_printf("(ctrl-c will return control to ddb)\n"); +#endif +} +#endif /* DDB */ Added: head/sys/gdb/netgdb.h ============================================================================== --- /dev/null 00:00:00 1970 (empty, because file is newly added) +++ head/sys/gdb/netgdb.h Thu Oct 17 21:33:01 2019 (r353700) @@ -0,0 +1,44 @@ +/*- + * SPDX-License-Identifier: BSD-2-Clause-FreeBSD + * + * Copyright (c) 2019 Isilon Systems, LLC. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + * + * $FreeBSD$ + */ +#pragma once + +/* + * Protocol information, for use by the userspace proxy server. + * + * It might make sense to allow not hardcoding these parameters as future work + * (e.g., for use in environments with arbitrary port filtering). + * + * The herald port is only used for initial handshake. The proxy server will + * choose a different remote port to connect back to the NetGDB client on by + * sending the HERALD ACK from that other port. + */ +#define NETGDB_HERALDPORT 20025 +#define NETGDB_CLIENTPORT 20026 + +#define NETGDB_PROTO_V1 0x2515f095 /* Rolled a 2^32 sided die. */ Modified: head/sys/i386/conf/GENERIC ============================================================================== --- head/sys/i386/conf/GENERIC Thu Oct 17 21:25:50 2019 (r353699) +++ head/sys/i386/conf/GENERIC Thu Oct 17 21:33:01 2019 (r353700) @@ -101,6 +101,7 @@ options GZIO # gzip-compressed kernel and user dump options ZSTDIO # zstd-compressed kernel and user dumps options DEBUGNET # debugnet networking options NETDUMP # netdump(4) client support +options NETGDB # netgdb(4) client support # To make an SMP kernel, the next two lines are needed options SMP # Symmetric MultiProcessor Kernel Modified: head/sys/kern/subr_kdb.c ============================================================================== --- head/sys/kern/subr_kdb.c Thu Oct 17 21:25:50 2019 (r353699) +++ head/sys/kern/subr_kdb.c Thu Oct 17 21:33:01 2019 (r353700) @@ -77,7 +77,6 @@ static int kdb_break_to_debugger = KDB_BREAK_TO_DEBUGG static int kdb_alt_break_to_debugger = KDB_ALT_BREAK_TO_DEBUGGER; KDB_BACKEND(null, NULL, NULL, NULL, NULL); -SET_DECLARE(kdb_dbbe_set, struct kdb_dbbe); static int kdb_sysctl_available(SYSCTL_HANDLER_ARGS); static int kdb_sysctl_current(SYSCTL_HANDLER_ARGS); Modified: head/sys/net/debugnet.c ============================================================================== --- head/sys/net/debugnet.c Thu Oct 17 21:25:50 2019 (r353699) +++ head/sys/net/debugnet.c Thu Oct 17 21:33:01 2019 (r353700) @@ -183,7 +183,7 @@ debugnet_udp_output(struct debugnet_pcb *pcb, struct m return (debugnet_ip_output(pcb, m)); } -static int +int debugnet_ack_output(struct debugnet_pcb *pcb, uint32_t seqno /* net endian */) { struct debugnet_ack *dn_ack; @@ -330,7 +330,7 @@ retransmit: printf(". "); goto retransmit; } - debugnet_network_poll(pcb->dp_ifp); + debugnet_network_poll(pcb); DELAY(500); if (pcb->dp_state == DN_STATE_REMOTE_CLOSED) return (ECONNRESET); @@ -577,8 +577,11 @@ done: * driver directly for packets. */ void -debugnet_network_poll(struct ifnet *ifp) +debugnet_network_poll(struct debugnet_pcb *pcb) { + struct ifnet *ifp; + + ifp = pcb->dp_ifp; ifp->if_debugnet_methods->dn_poll(ifp, 1000); } @@ -610,6 +613,7 @@ int debugnet_connect(const struct debugnet_conn_params *dcp, struct debugnet_pcb **pcb_out) { + struct debugnet_proto_aux herald_auxdata; struct debugnet_pcb *pcb; struct ifnet *ifp; int error; @@ -738,8 +742,12 @@ debugnet_connect(const struct debugnet_conn_params *dc } MPASS(pcb->dp_state == DN_STATE_HAVE_GW_MAC); + herald_auxdata = (struct debugnet_proto_aux) { + .dp_offset_start = dcp->dc_herald_offset, + .dp_aux2 = dcp->dc_herald_aux2, + }; error = debugnet_send(pcb, DEBUGNET_HERALD, dcp->dc_herald_data, - dcp->dc_herald_datalen, NULL); + dcp->dc_herald_datalen, &herald_auxdata); if (error != 0) { printf("%s: failed to herald debugnet server\n", __func__); goto cleanup; Modified: head/sys/net/debugnet.h ============================================================================== --- head/sys/net/debugnet.h Thu Oct 17 21:25:50 2019 (r353699) +++ head/sys/net/debugnet.h Thu Oct 17 21:33:01 2019 (r353700) @@ -108,6 +108,14 @@ struct debugnet_conn_params { uint32_t dc_herald_datalen; /* + * Consistent with debugnet_send(), aux paramaters to debugnet + * functions are provided host-endian (but converted to + * network endian on the wire). + */ + uint32_t dc_herald_aux2; + uint64_t dc_herald_offset; + + /* * If NULL, debugnet is a unidirectional channel from panic machine to * remote server (like netdump). * @@ -123,12 +131,14 @@ struct debugnet_conn_params { * If the handler frees the mbuf chain, it should set the mbuf pointer * to NULL. Otherwise, the debugnet input framework will free the * chain. + * + * The handler should ACK receieved packets with debugnet_ack_output. */ void (*dc_rx_handler)(struct debugnet_pcb *, struct mbuf **); }; /* - * Open a unidirectional stream to the specified server's herald port. + * Open a stream to the specified server's herald port. * * If all goes well, the server will send ACK from a different port to our ack * port. This allows servers to somewhat gracefully handle multiple debugnet @@ -176,6 +186,16 @@ debugnet_sendempty(struct debugnet_pcb *pcb, uint32_t *** DIFF OUTPUT TRUNCATED AT 1000 LINES ***
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