anchao commented on code in PR #7616:
URL: https://github.com/apache/nuttx/pull/7616#discussion_r1037774072
##########
mm/iob/Kconfig:
##########
@@ -41,7 +41,7 @@ config IOB_HEADSIZE
config IOB_ALIGNMENT
int "Alignment size of each I/O buffer"
- default 1
+ default 4
Review Comment:
Because many fields in the l3 protocol are defined by 4 bytes, in order to
avoid unaligned access, the default value is changed to 4 bytes
```
struct ipv4_hdr_s
{
uint8_t vhl; /* 8-bit Version (4) and header length (5 or
6) */
uint8_t tos; /* 8-bit Type of service (e.g., 6=TCP) */
uint8_t len[2]; /* 16-bit Total length */
uint8_t ipid[2]; /* 16-bit Identification */
uint8_t ipoffset[2]; /* 16-bit IP flags + fragment offset */
uint8_t ttl; /* 8-bit Time to Live */
uint8_t proto; /* 8-bit Protocol */
uint16_t ipchksum; /* 16-bit Header checksum */
uint16_t srcipaddr[2]; /* 32-bit Source IP address */
uint16_t destipaddr[2]; /* 32-bit Destination IP address */
};
typedef uint16_t net_ipv6addr_t[8];
struct ipv6_hdr_s
{
uint8_t vtc; /* Bits 0-3: version, bits 4-7: traffic class
(MS) */
uint8_t tcf; /* Bits 0-3: traffic class (LS), 4-bits: flow
label (MS) */
uint16_t flow; /* 16-bit flow label (LS) */
uint8_t len[2]; /* 16-bit Payload length */
uint8_t proto; /* 8-bit Next header (same as IPv4 protocol
field) */
uint8_t ttl; /* 8-bit Hop limit (like IPv4 TTL field) */
net_ipv6addr_t srcipaddr; /* 128-bit Source address */
net_ipv6addr_t destipaddr; /* 128-bit Destination address */
};
```
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