[RFC PATCH 3/6] export: Implement logic behind reexport=

[Richard Weinberger <richard@nod.at>]

This covers the cross mount case. When mountd/exportd detect
a cross mount on a re-exported NFS volume a identifier has to
be found to make nfsd happy.

Signed-off-by: Richard Weinberger <richard@nod.at>
---
 support/export/Makefile.am |   2 +
 support/export/cache.c     | 140 +++++++++++++++++++++++++++++++++----
 utils/exportd/Makefile.am  |   8 ++-
 utils/exportd/exportd.c    |   2 +
 utils/mountd/Makefile.am   |   6 ++
 5 files changed, 144 insertions(+), 14 deletions(-)

diff --git a/support/export/Makefile.am b/support/export/Makefile.am
index eec737f6..90109b1e 100644
--- a/support/export/Makefile.am
+++ b/support/export/Makefile.am
@@ -14,6 +14,8 @@ libexport_a_SOURCES = client.c export.c hostname.c \
 		      xtab.c mount_clnt.c mount_xdr.c \
 		      cache.c auth.c v4root.c fsloc.c \
 		      v4clients.c
+libexport_a_CPPFLAGS = -I$(top_srcdir)/support/reexport
+
 BUILT_SOURCES 	= $(GENFILES)
 
 noinst_HEADERS = mount.h
diff --git a/support/export/cache.c b/support/export/cache.c
index a5823e92..6039745e 100644
--- a/support/export/cache.c
+++ b/support/export/cache.c
@@ -33,6 +33,7 @@
 #include "export.h"
 #include "pseudoflavors.h"
 #include "xcommon.h"
+#include "reexport.h"
 
 #ifdef HAVE_JUNCTION_SUPPORT
 #include "fsloc.h"
@@ -235,6 +236,16 @@ static void auth_unix_gid(int f)
 		xlog(L_ERROR, "auth_unix_gid: error writing reply");
 }
 
+static int match_crossmnt_fsidnum(uint32_t parsed_fsidnum, char *path)
+{
+	uint32_t fsidnum;
+
+	if (reexpdb_fsidnum_by_path(path, &fsidnum, 0) == 0)
+		return 0;
+
+	return fsidnum == parsed_fsidnum;
+}
+
 #ifdef USE_BLKID
 static const char *get_uuid_blkdev(char *path)
 {
@@ -331,7 +342,52 @@ static const unsigned long nonblkid_filesystems[] = {
     0        /* last */
 };
 
-static int uuid_by_path(char *path, int type, size_t uuidlen, char *uuid)
+static int get_uuid_from_fsid(char *path, char *uuid_str, size_t len)
+{
+	unsigned int min_dev, maj_dev, min_fsid, maj_fsid;
+	int rc, n, found = 0, header_seen = 0;
+	struct stat stb;
+	FILE *nfsfs_fd;
+	char line[128];
+
+	rc = nfsd_path_stat(path, &stb);
+	if (rc) {
+		xlog(L_WARNING, "Unable to stat %s", path);
+		return 0;
+	}
+
+	nfsfs_fd = fopen("/proc/fs/nfsfs/volumes", "r");
+	if (nfsfs_fd == NULL) {
+		xlog(L_WARNING, "Unable to open nfsfs volume file: %m");
+		return 0;
+	}
+
+	while (fgets(line, sizeof(line), nfsfs_fd) != NULL) {
+		if (!header_seen) {
+			header_seen = 1;
+			continue;
+		}
+		n = sscanf(line, "v%*u %*x %*u %u:%u %x:%x %*s", &maj_dev,
+			   &min_dev, &maj_fsid, &min_fsid);
+
+		if (n != 4) {
+			xlog(L_WARNING, "Unable to parse nfsfs volume line: %d, %s", n, line);
+			continue;
+		}
+
+		if (makedev(maj_dev, min_dev) == stb.st_dev) {
+			found = 1;
+			snprintf(uuid_str, len, "%08x%08x", maj_fsid, min_fsid);
+			break;
+		}
+	}
+
+	fclose(nfsfs_fd);
+
+	return found;
+}
+
+static int uuid_by_path(struct exportent *exp, char *path, int type, size_t uuidlen, char *uuid)
 {
 	/* get a uuid for the filesystem found at 'path'.
 	 * There are several possible ways of generating the
@@ -362,7 +418,7 @@ static int uuid_by_path(char *path, int type, size_t uuidlen, char *uuid)
 	 */
 	struct statfs64 st;
 	char fsid_val[17];
-	const char *blkid_val = NULL;
+	const char *fsuuid_val = NULL;
 	const char *val;
 	int rc;
 
@@ -375,7 +431,20 @@ static int uuid_by_path(char *path, int type, size_t uuidlen, char *uuid)
 				break;
 		}
 		if (*bad == 0)
-			blkid_val = get_uuid_blkdev(path);
+			fsuuid_val = get_uuid_blkdev(path);
+		else if (exp->e_reexport == REEXP_REMOTE_DEVFSID &&
+			 *bad == 0x6969 /* NFS_SUPER_MAGIC */) {
+			char tmp[17];
+			int ret = get_uuid_from_fsid(path, tmp, sizeof(tmp));
+
+			if (ret < 0) {
+				xlog(L_WARNING, "Unable to read nfsfs volume file: %i", ret);
+			} else if (ret == 0) {
+				xlog(L_WARNING, "Unable to find nfsfs volume entry for %s", path);
+			} else {
+				fsuuid_val = tmp;
+			}
+		}
 	}
 
 	if (rc == 0 &&
@@ -385,8 +454,8 @@ static int uuid_by_path(char *path, int type, size_t uuidlen, char *uuid)
 	else
 		fsid_val[0] = 0;
 
-	if (blkid_val && (type--) == 0)
-		val = blkid_val;
+	if (fsuuid_val && (type--) == 0)
+		val = fsuuid_val;
 	else if (fsid_val[0] && (type--) == 0)
 		val = fsid_val;
 	else
@@ -684,8 +753,13 @@ static int match_fsid(struct parsed_fsid *parsed, nfs_export *exp, char *path)
 		goto match;
 	case FSID_NUM:
 		if (((exp->m_export.e_flags & NFSEXP_FSID) == 0 ||
-		     exp->m_export.e_fsid != parsed->fsidnum))
+		     exp->m_export.e_fsid != parsed->fsidnum)) {
+			if (exp->m_export.e_flags & NFSEXP_CROSSMOUNT &&
+			    match_crossmnt_fsidnum(parsed->fsidnum, path))
+				goto match;
+
 			goto nomatch;
+		}
 		goto match;
 	case FSID_UUID4_INUM:
 	case FSID_UUID16_INUM:
@@ -708,7 +782,7 @@ static int match_fsid(struct parsed_fsid *parsed, nfs_export *exp, char *path)
 		}
 		else
 			for (type = 0;
-			     uuid_by_path(path, type, parsed->uuidlen, u);
+			     uuid_by_path(&exp->m_export, path, type, parsed->uuidlen, u);
 			     type++)
 				if (memcmp(u, parsed->fhuuid, parsed->uuidlen) == 0)
 					goto match;
@@ -932,7 +1006,7 @@ static void write_fsloc(char **bp, int *blen, struct exportent *ep)
 	release_replicas(servers);
 }
 #endif
-static void write_secinfo(char **bp, int *blen, struct exportent *ep, int flag_mask)
+static void write_secinfo(char **bp, int *blen, struct exportent *ep, int flag_mask, int extra_flag)
 {
 	struct sec_entry *p;
 
@@ -947,11 +1021,20 @@ static void write_secinfo(char **bp, int *blen, struct exportent *ep, int flag_m
 	qword_addint(bp, blen, p - ep->e_secinfo);
 	for (p = ep->e_secinfo; p->flav; p++) {
 		qword_addint(bp, blen, p->flav->fnum);
-		qword_addint(bp, blen, p->flags & flag_mask);
+		qword_addint(bp, blen, (p->flags | extra_flag) & flag_mask);
 	}
 
 }
 
+static int can_reexport_via_fsidnum(struct exportent *exp, struct statfs64 *st)
+{
+	if (st->f_type != 0x6969 /* NFS_SUPER_MAGIC */)
+		return 0;
+
+	return exp->e_reexport == REEXP_PREDEFINED_FSIDNUM ||
+	       exp->e_reexport == REEXP_AUTO_FSIDNUM;
+}
+
 static int dump_to_cache(int f, char *buf, int blen, char *domain,
 			 char *path, struct exportent *exp, int ttl)
 {
@@ -968,21 +1051,52 @@ static int dump_to_cache(int f, char *buf, int blen, char *domain,
 	if (exp) {
 		int different_fs = strcmp(path, exp->e_path) != 0;
 		int flag_mask = different_fs ? ~NFSEXP_FSID : ~0;
+		int rc, do_fsidnum = 0;
+		uint32_t fsidnum = exp->e_fsid;
+
+		if (different_fs) {
+			struct statfs64 st;
+	
+			rc = nfsd_path_statfs64(path, &st);
+			if (rc) {
+				xlog(L_WARNING, "unable to statfs %s", path);
+				errno = EINVAL;
+				return -1;
+			}
+
+			if (can_reexport_via_fsidnum(exp, &st)) {
+				do_fsidnum = 1;
+				flag_mask = ~0;
+			}
+		}
 
 		qword_adduint(&bp, &blen, now + exp->e_ttl);
-		qword_addint(&bp, &blen, exp->e_flags & flag_mask);
+
+		if (do_fsidnum) {
+			uint32_t search_fsidnum = 0;
+			if (reexpdb_fsidnum_by_path(path, &search_fsidnum,
+			    exp->e_reexport == REEXP_AUTO_FSIDNUM) == 0) {
+				errno = EINVAL;
+				return -1;
+			}
+			fsidnum = search_fsidnum;
+			qword_addint(&bp, &blen, exp->e_flags | NFSEXP_FSID);
+		} else {
+			qword_addint(&bp, &blen, exp->e_flags & flag_mask);
+		}
+
 		qword_addint(&bp, &blen, exp->e_anonuid);
 		qword_addint(&bp, &blen, exp->e_anongid);
-		qword_addint(&bp, &blen, exp->e_fsid);
+		qword_addint(&bp, &blen, fsidnum);
 
 #ifdef HAVE_JUNCTION_SUPPORT
 		write_fsloc(&bp, &blen, exp);
 #endif
-		write_secinfo(&bp, &blen, exp, flag_mask);
+		write_secinfo(&bp, &blen, exp, flag_mask, do_fsidnum ? NFSEXP_FSID : 0);
 		if (exp->e_uuid == NULL || different_fs) {
 			char u[16];
 			if ((exp->e_flags & flag_mask & NFSEXP_FSID) == 0 &&
-			    uuid_by_path(path, 0, 16, u)) {
+			    uuid_by_path(exp, path, 0, 16, u)) {
 				qword_add(&bp, &blen, "uuid");
 				qword_addhex(&bp, &blen, u, 16);
 			}
diff --git a/utils/exportd/Makefile.am b/utils/exportd/Makefile.am
index c95bdee7..b0ec9034 100644
--- a/utils/exportd/Makefile.am
+++ b/utils/exportd/Makefile.am
@@ -16,11 +16,17 @@ exportd_SOURCES = exportd.c
 exportd_LDADD = ../../support/export/libexport.a \
 			../../support/nfs/libnfs.la \
 			../../support/misc/libmisc.a \
-			$(OPTLIBS) $(LIBBLKID) $(LIBPTHREAD) -luuid
+			$(OPTLIBS) $(LIBBLKID) $(LIBPTHREAD) \
+			-luuid
+if CONFIG_REEXPORT
+exportd_LDADD += ../../support/reexport/libreexport.a $(LIBSQLITE) -lrt
+endif
 
 exportd_CPPFLAGS = $(AM_CPPFLAGS) $(CPPFLAGS) \
 		-I$(top_srcdir)/support/export
 
+exportd_CPPFLAGS += -I$(top_srcdir)/support/reexport
+
 MAINTAINERCLEANFILES = Makefile.in
 
 #######################################################################
diff --git a/utils/exportd/exportd.c b/utils/exportd/exportd.c
index 2dd12cb6..4ddfed35 100644
--- a/utils/exportd/exportd.c
+++ b/utils/exportd/exportd.c
@@ -22,6 +22,7 @@
 #include "conffile.h"
 #include "exportfs.h"
 #include "export.h"
+#include "reexport.h"
 
 extern void my_svc_run(void);
 
@@ -296,6 +297,7 @@ main(int argc, char **argv)
 	/* Open files now to avoid sharing descriptors among forked processes */
 	cache_open();
 	v4clients_init();
+	reexpdb_init();
 
 	/* Process incoming upcalls */
 	cache_process_loop();
diff --git a/utils/mountd/Makefile.am b/utils/mountd/Makefile.am
index 13b25c90..569d335a 100644
--- a/utils/mountd/Makefile.am
+++ b/utils/mountd/Makefile.am
@@ -20,10 +20,16 @@ mountd_LDADD = ../../support/export/libexport.a \
 	       $(OPTLIBS) \
 	       $(LIBBSD) $(LIBWRAP) $(LIBNSL) $(LIBBLKID) -luuid $(LIBTIRPC) \
 	       $(LIBPTHREAD)
+if CONFIG_REEXPORT
+mountd_LDADD += ../../support/reexport/libreexport.a $(LIBSQLITE) -lrt
+endif
+
 mountd_CPPFLAGS = $(AM_CPPFLAGS) $(CPPFLAGS) \
 		  -I$(top_builddir)/support/include \
 		  -I$(top_srcdir)/support/export
 
+mountd_CPPFLAGS += -I$(top_srcdir)/support/reexport
+
 MAINTAINERCLEANFILES = Makefile.in
 
 #######################################################################
-- 
2.31.1