[PATCH v4] lib/net: add MPLS insert and strip functionality

[Tanzeel-inline <tanxeel1.ahmed@gmail.com>]

From: Tanzeel Ahmed <tanxeel1.ahmed@gmail.com>

This patch is new version of [PATCH] lib/net: added push MPLS header API.
I have also added the MPLS strip functionality to address the question
asked in last patch.

> You should explain why you add this function.
None of the foundational NICs currently supports MPLS insertion and
stripping, this functionality can help users who rely on MPLS in their
network application.

> I'm not sure it should be inline
I did for performance in high-traffic application.

Signed-off-by: Tanzeel Ahmed <tanxeel1.ahmed@gmail.com>

---
v4:
* Removed extra void cast.
* rte_pktmbuf_append/mtod now return void*.
  The memmove result is casted to rte_ether_hdr*.

v3:
* fixed patch check failure issue

v2:
* marked experimental
* coding style fixed
* changed rte_memcpy to memcpy
* mpls header marked as const in parameter
* added MPLS stripping functionality
---
 .mailmap           |  1 +
 lib/net/rte_mpls.h | 97 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 98 insertions(+)

diff --git a/.mailmap b/.mailmap
index a9f4f28..2af4e0d 100644
--- a/.mailmap
+++ b/.mailmap
@@ -1312,6 +1312,7 @@ Takeshi Yoshimura <tyos@jp.ibm.com> <t.yoshimura8869@gmail.com>
 Takuya Asada <syuu@cloudius-systems.com>
 Tal Avraham <talavr@annapurnalabs.com>
 Tal Shnaiderman <talshn@nvidia.com> <talshn@mellanox.com>
+Tanzeel Ahmed <tanxeel1.ahmed@gmail.com>
 Tao Y Yang <tao.y.yang@intel.com>
 Tao Zhu <taox.zhu@intel.com>
 Taripin Samuel <samuel.taripin@intel.com>
diff --git a/lib/net/rte_mpls.h b/lib/net/rte_mpls.h
index 51523e7..d7e267f 100644
--- a/lib/net/rte_mpls.h
+++ b/lib/net/rte_mpls.h
@@ -13,6 +13,8 @@
 
 #include <stdint.h>
 #include <rte_byteorder.h>
+#include <rte_ether.h>
+#include <rte_mbuf.h>
 
 #ifdef __cplusplus
 extern "C" {
@@ -36,6 +38,101 @@ struct rte_mpls_hdr {
 	uint8_t  ttl;       /**< Time to live. */
 } __rte_packed;
 
+#define RTE_MPLS_HLEN 4 /**< Length of MPLS header. */
+
+/**
+ * @warning
+ * @b EXPERIMENTAL: this API may change without prior notice.
+ *
+ * Insert MPLS header into the packet.
+ * If it's first MPLS header to be inserted in the packet,
+ *  - Updates the ether type.
+ *  - Sets the MPLS bottom-of-stack bit to 1.
+ *
+ * @param m
+ *   The pointer to the mbuf.
+ * @param mp
+ *   The pointer to the MPLS header.
+ * @return
+ *   0 on success, -1 on error
+ */
+__rte_experimental
+static inline int
+rte_mpls_push_over_l2(struct rte_mbuf **m, const struct rte_mpls_hdr *mp)
+{
+	void *os, *ns;
+	struct rte_ether_hdr *nh;
+	struct rte_mpls_hdr *mph;
+
+	/* Can't insert header if mbuf is shared */
+	if (!RTE_MBUF_DIRECT(*m) || rte_mbuf_refcnt_read(*m) > 1)
+		return -EINVAL;
+
+	/* Can't insert header if ethernet frame doesn't exist */
+	if (rte_pktmbuf_data_len(*m) < RTE_ETHER_HDR_LEN)
+		return -EINVAL;
+
+	os = rte_pktmbuf_mtod(*m, void *);
+	ns = (void *)rte_pktmbuf_prepend(*m, sizeof(struct rte_mpls_hdr));
+	if (ns == NULL)
+		return -ENOSPC;
+
+	nh = (struct rte_ether_hdr *)memmove(ns, os, RTE_ETHER_HDR_LEN);
+
+	/* Copy the MPLS header after ethernet frame */
+	mph = rte_pktmbuf_mtod_offset(*m, struct rte_mpls_hdr*,
+			sizeof(struct rte_ether_hdr));
+	memcpy(mph, mp, RTE_MPLS_HLEN);
+
+	mph->tag_msb = rte_cpu_to_be_16(mp->tag_msb);
+
+	/* If first MPLS header, update ether type and bottom-of-stack bit */
+	if (nh->ether_type != rte_cpu_to_be_16(RTE_ETHER_TYPE_MPLS)) {
+		nh->ether_type = rte_cpu_to_be_16(RTE_ETHER_TYPE_MPLS);
+		mph->bs = 1;
+	} else {
+		mph->bs = 0;
+	}
+
+	return 0;
+}
+
+/**
+ * @warning
+ * @b EXPERIMENTAL: this API may change without prior notice.
+ *
+ * Strips MPLS from the packet. Doesn't update the ether type
+ *
+ * @param m
+ *   The pointer to the mbuf.
+ * @return
+ *   0 on success, -1 on error
+ */
+__rte_experimental
+static inline int
+rte_mpls_strip_over_l2(struct rte_mbuf *m)
+{
+	struct rte_ether_hdr *eh = rte_pktmbuf_mtod(m, struct rte_ether_hdr *);
+	struct rte_mpls_hdr *mph;
+	bool mpls_exist = true;
+
+	if (eh->ether_type != rte_cpu_to_be_16(RTE_ETHER_TYPE_MPLS))
+		return -1;
+
+	/* Stripping all MPLS header */
+	while (mpls_exist) {
+		mph = rte_pktmbuf_mtod_offset(m, struct rte_mpls_hdr*,
+		sizeof(struct rte_ether_hdr));
+		if (mph->bs & 1)
+			mpls_exist = false;
+		memmove(rte_pktmbuf_adj(m, sizeof(struct rte_mpls_hdr)),
+		eh, sizeof(struct rte_ether_hdr));
+		eh = rte_pktmbuf_mtod(m, struct rte_ether_hdr *);
+	}
+
+	return 0;
+}
+
 #ifdef __cplusplus
 }
 #endif
-- 
1.8.3.1