[PATCH] ip_frag: add fragmenting IPv4 header optional field

[Huichao Cai <chcchc88@163.com>]

According to RFC791,the options may appear or not in datagrams.
They must be implemented by all IP modules (host and gateways).
What is optional is their transmission in any particular datagram,
not their implementation.So we have to deal with it during the
fragmenting process.

Signed-off-by: Huichao Cai <chcchc88@163.com>
---
 lib/ip_frag/rte_ipv4_fragmentation.c | 52 +++++++++++++++++++++++++++++++++++-
 1 file changed, 51 insertions(+), 1 deletion(-)

diff --git a/lib/ip_frag/rte_ipv4_fragmentation.c b/lib/ip_frag/rte_ipv4_fragmentation.c
index 2e7739d..bcafa29 100644
--- a/lib/ip_frag/rte_ipv4_fragmentation.c
+++ b/lib/ip_frag/rte_ipv4_fragmentation.c
@@ -1,4 +1,4 @@
-/* SPDX-License-Identifier: BSD-3-Clause
+/* SPDX-License-Identifier: (BSD-3-Clause OR GPL-2.0)
  * Copyright(c) 2010-2014 Intel Corporation
  */
 
@@ -12,6 +12,13 @@
 
 #include "ip_frag_common.h"
 
+/* IP options */
+#define RTE_IPOPT_COPY				0x80
+#define RTE_IPOPT_CONTROL			0x00
+#define RTE_IPOPT_END				(0 | RTE_IPOPT_CONTROL)
+#define RTE_IPOPT_NOOP				(1 | RTE_IPOPT_CONTROL)
+#define RTE_IPOPT_COPIED(o)			((o) & RTE_IPOPT_COPY)
+
 /* Fragment Offset */
 #define	RTE_IPV4_HDR_DF_SHIFT			14
 #define	RTE_IPV4_HDR_MF_SHIFT			13
@@ -41,6 +48,38 @@ static inline void __free_fragments(struct rte_mbuf *mb[], uint32_t num)
 		rte_pktmbuf_free(mb[i]);
 }
 
+/*
+ *	Options "fragmenting", just fill options not
+ *	allowed in fragments with NOOPs.
+ *	Simple and stupid 8), but the most efficient way.
+ */
+static inline void ip_options_fragment(struct rte_ipv4_hdr *iph)
+{
+	unsigned char *optptr = (unsigned char *)iph +
+	    sizeof(struct rte_ipv4_hdr);
+	int l = (iph->version_ihl & RTE_IPV4_HDR_IHL_MASK) *
+	    RTE_IPV4_IHL_MULTIPLIER - sizeof(struct rte_ipv4_hdr);
+	int optlen;
+
+	while (l > 0) {
+		switch (*optptr) {
+		case RTE_IPOPT_END:
+			return;
+		case RTE_IPOPT_NOOP:
+			l--;
+			optptr++;
+			continue;
+		}
+		optlen = optptr[1];
+		if (optlen < 2 || optlen > l)
+			return;
+		if (!RTE_IPOPT_COPIED(*optptr))
+			memset(optptr, RTE_IPOPT_NOOP, optlen);
+		l -= optlen;
+		optptr += optlen;
+	}
+}
+
 /**
  * IPv4 fragmentation.
  *
@@ -188,6 +227,17 @@ static inline void __free_fragments(struct rte_mbuf *mb[], uint32_t num)
 		    (uint16_t)out_pkt->pkt_len,
 		    flag_offset, fragment_offset, more_in_segs);
 
+		/*
+		 * ANK: dirty, but effective trick. Upgrade options only if
+		 * the segment to be fragmented was THE FIRST (otherwise,
+		 * options are already fixed) and make it ONCE
+		 * on the initial mbuf, so that all the following fragments
+		 * will inherit fixed options.
+		 */
+		if ((fragment_offset == 0) &&
+			    ((flag_offset & RTE_IPV4_HDR_OFFSET_MASK) == 0))
+			ip_options_fragment(in_hdr);
+
 		fragment_offset = (uint16_t)(fragment_offset +
 		    out_pkt->pkt_len - header_len);
 
-- 
1.8.3.1