diff --git a/packages/cstruct-async/cstruct-async.6.1.0/opam b/packages/cstruct-async/cstruct-async.6.1.0/opam
new file mode 100644
index 000000000000..f0d3ca5fa903
--- /dev/null
+++ b/packages/cstruct-async/cstruct-async.6.1.0/opam
@@ -0,0 +1,37 @@
+opam-version: "2.0"
+maintainer:   "anil@recoil.org"
+authors:      ["Anil Madhavapeddy" "Richard Mortier" "Thomas Gazagnaire"
+               "Pierre Chambart" "David Kaloper" "Jeremy Yallop" "David Scott"
+               "Mindy Preston" "Thomas Leonard" "Etienne Millon" ]
+homepage:     "https://github.com/mirage/ocaml-cstruct"
+license:      "ISC"
+dev-repo: "git+https://github.com/mirage/ocaml-cstruct.git"
+bug-reports:  "https://github.com/mirage/ocaml-cstruct/issues"
+tags: [ "org:mirage" "org:ocamllabs" ]
+doc: "https://mirage.github.io/ocaml-cstruct/"
+build: [
+  ["dune" "subst"] {dev}
+  ["dune" "build" "-p" name "-j" jobs]
+]
+depends: [
+  "ocaml" {>= "4.08.0"}
+  "dune" {>= "2.0.0"}
+  "async" {>= "v0.9.0"}
+  "async_unix" {>= "v0.9.0"}
+  "core" {>= "v0.9.0"}
+  "cstruct" {=version}
+]
+synopsis: "Access C-like structures directly from OCaml"
+description: """
+Cstruct is a library and syntax extension to make it easier to access C-like
+structures directly from OCaml.  It supports both reading and writing to these
+structures, and they are accessed via the `Bigarray` module."""
+url {
+  src:
+    "https://github.com/mirage/ocaml-cstruct/releases/download/v6.1.0/cstruct-6.1.0.tbz"
+  checksum: [
+    "sha256=9dd9f9b5148829edf65b811df981c4368a02aef98d93aa388345e8a23a49f084"
+    "sha512=1f6a2ddb395bdd2f50840a96202e5aa64c68d1a7371340ca1982cc7a40ba213ffbea64864999cff3d5a8790b4f45d211f25c97ce268617bea5050443b3600c68"
+  ]
+}
+x-commit-hash: "5472fb9e968b7914eed22b7d20882acb2a402d8d"
diff --git a/packages/cstruct-lwt/cstruct-lwt.6.1.0/opam b/packages/cstruct-lwt/cstruct-lwt.6.1.0/opam
new file mode 100644
index 000000000000..f1076fbe5963
--- /dev/null
+++ b/packages/cstruct-lwt/cstruct-lwt.6.1.0/opam
@@ -0,0 +1,36 @@
+opam-version: "2.0"
+maintainer:   "anil@recoil.org"
+authors:      ["Anil Madhavapeddy" "Richard Mortier" "Thomas Gazagnaire"
+               "Pierre Chambart" "David Kaloper" "Jeremy Yallop" "David Scott"
+               "Mindy Preston" "Thomas Leonard" "Etienne Millon" ]
+homepage:     "https://github.com/mirage/ocaml-cstruct"
+license:      "ISC"
+dev-repo: "git+https://github.com/mirage/ocaml-cstruct.git"
+bug-reports:  "https://github.com/mirage/ocaml-cstruct/issues"
+doc: "https://mirage.github.io/ocaml-cstruct/"
+tags: [ "org:mirage" "org:ocamllabs" ]
+build: [
+  ["dune" "subst"] {dev}
+  ["dune" "build" "-p" name "-j" jobs]
+]
+depends: [
+  "ocaml" {>= "4.08.0"}
+  "base-unix"
+  "dune" {>= "2.0.0"}
+  "lwt"
+  "cstruct" {=version}
+]
+synopsis: "Access C-like structures directly from OCaml"
+description: """
+Cstruct is a library and syntax extension to make it easier to access C-like
+structures directly from OCaml.  It supports both reading and writing to these
+structures, and they are accessed via the `Bigarray` module."""
+url {
+  src:
+    "https://github.com/mirage/ocaml-cstruct/releases/download/v6.1.0/cstruct-6.1.0.tbz"
+  checksum: [
+    "sha256=9dd9f9b5148829edf65b811df981c4368a02aef98d93aa388345e8a23a49f084"
+    "sha512=1f6a2ddb395bdd2f50840a96202e5aa64c68d1a7371340ca1982cc7a40ba213ffbea64864999cff3d5a8790b4f45d211f25c97ce268617bea5050443b3600c68"
+  ]
+}
+x-commit-hash: "5472fb9e968b7914eed22b7d20882acb2a402d8d"
diff --git a/packages/cstruct-sexp/cstruct-sexp.6.1.0/opam b/packages/cstruct-sexp/cstruct-sexp.6.1.0/opam
new file mode 100644
index 000000000000..888c2c16f170
--- /dev/null
+++ b/packages/cstruct-sexp/cstruct-sexp.6.1.0/opam
@@ -0,0 +1,40 @@
+opam-version: "2.0"
+maintainer:   "anil@recoil.org"
+authors:      ["Anil Madhavapeddy" "Richard Mortier" "Thomas Gazagnaire"
+               "Pierre Chambart" "David Kaloper" "Jeremy Yallop" "David Scott"
+               "Mindy Preston" "Thomas Leonard" "Anton Kochkov" "Etienne Millon" ]
+homepage:     "https://github.com/mirage/ocaml-cstruct"
+license:      "ISC"
+dev-repo: "git+https://github.com/mirage/ocaml-cstruct.git"
+bug-reports:  "https://github.com/mirage/ocaml-cstruct/issues"
+doc: "https://mirage.github.io/ocaml-cstruct/"
+
+tags: [ "org:mirage" "org:ocamllabs" ]
+build: [
+  ["dune" "subst"] {dev}
+  ["dune" "build" "-p" name "-j" jobs]
+  ["dune" "runtest" "-p" name "-j" jobs] {with-test}
+]
+depends: [
+  "ocaml" {>= "4.08.0"}
+  "dune" {>= "2.0.0"}
+  "sexplib"
+  "cstruct" {=version}
+  "alcotest" {with-test}
+]
+synopsis: "S-expression serialisers for C-like structures"
+description: """
+Cstruct is a library and syntax extension to make it easier to access C-like
+structures directly from OCaml.  It supports both reading and writing to these
+structures, and they are accessed via the `Bigarray` module.
+
+This library provides Sexplib serialisers for the Cstruct.t values."""
+url {
+  src:
+    "https://github.com/mirage/ocaml-cstruct/releases/download/v6.1.0/cstruct-6.1.0.tbz"
+  checksum: [
+    "sha256=9dd9f9b5148829edf65b811df981c4368a02aef98d93aa388345e8a23a49f084"
+    "sha512=1f6a2ddb395bdd2f50840a96202e5aa64c68d1a7371340ca1982cc7a40ba213ffbea64864999cff3d5a8790b4f45d211f25c97ce268617bea5050443b3600c68"
+  ]
+}
+x-commit-hash: "5472fb9e968b7914eed22b7d20882acb2a402d8d"
diff --git a/packages/cstruct-unix/cstruct-unix.6.1.0/opam b/packages/cstruct-unix/cstruct-unix.6.1.0/opam
new file mode 100644
index 000000000000..fac5e4d4a712
--- /dev/null
+++ b/packages/cstruct-unix/cstruct-unix.6.1.0/opam
@@ -0,0 +1,39 @@
+opam-version: "2.0"
+maintainer:   "anil@recoil.org"
+authors:      ["Anil Madhavapeddy" "Richard Mortier" "Thomas Gazagnaire"
+               "Pierre Chambart" "David Kaloper" "Jeremy Yallop" "David Scott"
+               "Mindy Preston" "Thomas Leonard" "Etienne Millon" ]
+homepage:     "https://github.com/mirage/ocaml-cstruct"
+license:      "ISC"
+dev-repo: "git+https://github.com/mirage/ocaml-cstruct.git"
+bug-reports:  "https://github.com/mirage/ocaml-cstruct/issues"
+doc: "https://mirage.github.io/ocaml-cstruct/"
+
+tags: [ "org:mirage" "org:ocamllabs" ]
+build: [
+  ["dune" "subst"] {pinned}
+  ["dune" "build" "-p" name "-j" jobs]
+]
+depends: [
+  "ocaml" {>= "4.06.0"}
+  "dune" {>= "2.0.0"}
+  "base-unix"
+  "mmap" {>= "1.2.0"}
+  "cstruct" {=version}
+]
+synopsis: "Access C-like structures directly from OCaml"
+
+description: """
+Cstruct is a library and syntax extension to make it easier to access C-like
+structures directly from OCaml. It supports both reading and writing to these
+structures, and they are accessed via the `Bigarray` module.
+"""
+url {
+  src:
+    "https://github.com/mirage/ocaml-cstruct/releases/download/v6.1.0/cstruct-6.1.0.tbz"
+  checksum: [
+    "sha256=9dd9f9b5148829edf65b811df981c4368a02aef98d93aa388345e8a23a49f084"
+    "sha512=1f6a2ddb395bdd2f50840a96202e5aa64c68d1a7371340ca1982cc7a40ba213ffbea64864999cff3d5a8790b4f45d211f25c97ce268617bea5050443b3600c68"
+  ]
+}
+x-commit-hash: "5472fb9e968b7914eed22b7d20882acb2a402d8d"
diff --git a/packages/cstruct/cstruct.6.1.0/opam b/packages/cstruct/cstruct.6.1.0/opam
new file mode 100644
index 000000000000..8615bf8df444
--- /dev/null
+++ b/packages/cstruct/cstruct.6.1.0/opam
@@ -0,0 +1,39 @@
+opam-version: "2.0"
+maintainer:   "anil@recoil.org"
+authors:      ["Anil Madhavapeddy" "Richard Mortier" "Thomas Gazagnaire"
+               "Pierre Chambart" "David Kaloper" "Jeremy Yallop" "David Scott"
+               "Mindy Preston" "Thomas Leonard" "Anton Kochkov" "Etienne Millon" ]
+homepage:     "https://github.com/mirage/ocaml-cstruct"
+license:      "ISC"
+dev-repo: "git+https://github.com/mirage/ocaml-cstruct.git"
+bug-reports:  "https://github.com/mirage/ocaml-cstruct/issues"
+doc: "https://mirage.github.io/ocaml-cstruct/"
+
+tags: [ "org:mirage" "org:ocamllabs" ]
+build: [
+  ["dune" "subst"] {dev}
+  ["dune" "build" "-p" name "-j" jobs]
+  ["dune" "runtest" "-p" name "-j" jobs] {with-test}
+]
+depends: [
+  "ocaml" {>= "4.08.0"}
+  "dune" {>= "2.0.0"}
+  "alcotest" {with-test}
+  "fmt" {>= "0.8.9"}
+  "crowbar" {with-test}
+]
+conflicts: [ "js_of_ocaml" {<"3.5.0"} ]
+synopsis: "Access C-like structures directly from OCaml"
+description: """
+Cstruct is a library and syntax extension to make it easier to access C-like
+structures directly from OCaml.  It supports both reading and writing to these
+structures, and they are accessed via the `Bigarray` module."""
+url {
+  src:
+    "https://github.com/mirage/ocaml-cstruct/releases/download/v6.1.0/cstruct-6.1.0.tbz"
+  checksum: [
+    "sha256=9dd9f9b5148829edf65b811df981c4368a02aef98d93aa388345e8a23a49f084"
+    "sha512=1f6a2ddb395bdd2f50840a96202e5aa64c68d1a7371340ca1982cc7a40ba213ffbea64864999cff3d5a8790b4f45d211f25c97ce268617bea5050443b3600c68"
+  ]
+}
+x-commit-hash: "5472fb9e968b7914eed22b7d20882acb2a402d8d"
diff --git a/packages/ppx_cstruct/ppx_cstruct.6.1.0/opam b/packages/ppx_cstruct/ppx_cstruct.6.1.0/opam
new file mode 100644
index 000000000000..ea9dfc556e4d
--- /dev/null
+++ b/packages/ppx_cstruct/ppx_cstruct.6.1.0/opam
@@ -0,0 +1,46 @@
+opam-version: "2.0"
+maintainer:   "anil@recoil.org"
+authors:      ["Anil Madhavapeddy" "Richard Mortier" "Thomas Gazagnaire"
+               "Pierre Chambart" "David Kaloper" "Jeremy Yallop" "David Scott"
+               "Mindy Preston" "Thomas Leonard" "Etienne Millon" ]
+homepage:     "https://github.com/mirage/ocaml-cstruct"
+license:      "ISC"
+dev-repo: "git+https://github.com/mirage/ocaml-cstruct.git"
+bug-reports:  "https://github.com/mirage/ocaml-cstruct/issues"
+doc: "https://mirage.github.io/ocaml-cstruct/"
+
+tags: [ "org:mirage" "org:ocamllabs" ]
+build: [
+  ["dune" "subst"] {dev}
+  ["dune" "build" "-p" name "-j" jobs]
+  ["dune" "runtest" "-p" name "-j" jobs] {with-test}
+]
+depends: [
+  "ocaml" {>= "4.08.0"}
+  "dune" {>= "2.0.0"}
+  "cstruct" {=version}
+  "ounit" {with-test}
+  "ppxlib" {>= "0.16.0"}
+  "ppx_sexp_conv" {with-test}
+  "sexplib" {>="v0.9.0"}
+  "cstruct-sexp" {with-test}
+  "cppo" {with-test}
+  "cstruct-unix" {with-test & =version}
+  "stdlib-shims"
+  "ocaml-migrate-parsetree" {>= "2.1.0" & with-test}
+  "lwt_ppx" {>= "2.0.2" & with-test}
+]
+synopsis: "Access C-like structures directly from OCaml"
+description: """
+Cstruct is a library and syntax extension to make it easier to access C-like
+structures directly from OCaml.  It supports both reading and writing to these
+structures, and they are accessed via the `Bigarray` module."""
+url {
+  src:
+    "https://github.com/mirage/ocaml-cstruct/releases/download/v6.1.0/cstruct-6.1.0.tbz"
+  checksum: [
+    "sha256=9dd9f9b5148829edf65b811df981c4368a02aef98d93aa388345e8a23a49f084"
+    "sha512=1f6a2ddb395bdd2f50840a96202e5aa64c68d1a7371340ca1982cc7a40ba213ffbea64864999cff3d5a8790b4f45d211f25c97ce268617bea5050443b3600c68"
+  ]
+}
+x-commit-hash: "5472fb9e968b7914eed22b7d20882acb2a402d8d"