Add a helper to pad a short Ethernet frame to the minimum required
length, which can be used by backend codes.
Signed-off-by: Bin Meng <bmeng...@gmail.com>
---
Changes in v4:
- change 'ethernet' to 'Ethernet'
- do not inline the helper
- check the padded buffer size to avoid buffer overflow
Changes in v3:
- use 'without' instead of 'sans'
- add a helper to pad short frames
include/net/eth.h | 17 +++++++++++++++++
net/eth.c | 17 +++++++++++++++++
2 files changed, 34 insertions(+)
diff --git a/include/net/eth.h b/include/net/eth.h
index 0671be6916..6aabbdd0d3 100644
--- a/include/net/eth.h
+++ b/include/net/eth.h
@@ -31,6 +31,7 @@
#define ETH_ALEN 6
#define ETH_HLEN 14
+#define ETH_ZLEN 60 /* Min. octets in frame without FCS */
struct eth_header {
uint8_t h_dest[ETH_ALEN]; /* destination eth addr */
@@ -422,4 +423,20 @@ bool
eth_parse_ipv6_hdr(const struct iovec *pkt, int pkt_frags,
size_t ip6hdr_off, eth_ip6_hdr_info *info);
+/**
+ * eth_pad_short_frame - pad a short frame to the minimum Ethernet frame length
+ *
+ * If the Ethernet frame size is shorter than 60 bytes, it will be padded to
+ * 60 bytes at the address @padded_pkt.
+ *
+ * @padded_pkt: buffer address to hold the padded frame
+ * @padded_buflen: buffer length of @padded_pkt. If the frame is padded, it is
+ * written to ETH_ZLEN, otherwise it remains unchanged.
+ * @pkt: address to hold the original Ethernet frame
+ * @pkt_size: size of the original Ethernet frame
+ * @return true if the frame is padded, otherwise false
+ */
+bool eth_pad_short_frame(uint8_t *padded_pkt, size_t *padded_buflen,
+ const void *pkt, size_t pkt_size);
+
#endif
diff --git a/net/eth.c b/net/eth.c
index 1e0821c5f8..f913e4396f 100644
--- a/net/eth.c
+++ b/net/eth.c
@@ -548,3 +548,20 @@ bool eth_parse_ipv6_hdr(const struct iovec *pkt, int
pkt_frags,
info->l4proto = ext_hdr.ip6r_nxt;
return true;
}
+
+bool eth_pad_short_frame(uint8_t *padded_pkt, size_t *padded_buflen,
+ const void *pkt, size_t pkt_size)
+{
+ assert(padded_buflen && *padded_buflen >= ETH_ZLEN);
+
+ if (pkt_size >= ETH_ZLEN) {
+ return false;
+ }
+
+ /* pad to minimum Ethernet frame length */
+ memcpy(padded_pkt, pkt, pkt_size);
+ memset(&padded_pkt[pkt_size], 0, ETH_ZLEN - pkt_size);
+ *padded_buflen = ETH_ZLEN;
+
+ return true;
+}
--
2.25.1
