[PATCH 3/8] export: Wireup reexport mechanism

[Richard Weinberger <richard@xxxxxx>]

Detect the case when a NFS share is re-exported and assign an
fsidnum to it.
The fsidnum is read (or created) from the reexport database.

Signed-off-by: Richard Weinberger <richard@xxxxxx>
---
 support/export/cache.c | 68 ++++++++++++++++++++++++++++++++++++++----
 1 file changed, 62 insertions(+), 6 deletions(-)

diff --git a/support/export/cache.c b/support/export/cache.c
index 0a37703b..42a694d0 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)
 {
@@ -688,8 +699,13 @@ 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) && exp->m_export.e_reexport != REEXP_NONE &&
+			    match_crossmnt_fsidnum(parsed->fsidnum, path))
+				goto match;
+
 			goto nomatch;
+		}
 		goto match;
 	case FSID_UUID4_INUM:
 	case FSID_UUID16_INUM:
@@ -937,7 +953,7 @@ static void write_fsloc(char **bp, int *blen, struct exportent *ep)
 }
 #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;
 
@@ -952,7 +968,7 @@ 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);
 	}
 }
 
@@ -970,6 +986,15 @@ static void write_xprtsec(char **bp, int *blen, struct exportent *ep)
 		qword_addint(bp, blen, p->info->number);
 }
 
+static int can_reexport_via_fsidnum(struct exportent *exp, struct statfs *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)
 {
@@ -986,17 +1011,48 @@ 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 statfs st;
+
+			rc = nfsd_path_statfs(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 (exp->e_reexport != REEXP_NONE && 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 &&
-- 
2.31.1