check the length of IPv4 packet info control messages, add log message (#3920)

sys_conn_oob.go

@@ -6,8 +6,10 @@ import (
 	"encoding/binary"
 	"errors"
 	"fmt"
+	"log"
 	"net"
 	"net/netip"
+	"sync"
 	"syscall"
 	"time"
 
@@ -149,6 +151,8 @@ func newConn(c OOBCapablePacketConn, supportsDF bool) (*oobConn, error) {
 	return oobConn, nil
 }
 
+var invalidCmsgOnceV4, invalidCmsgOnceV6 sync.Once
+
 func (c *oobConn) ReadPacket() (receivedPacket, error) {
 	if len(c.messages) == int(c.readPos) { // all messages read. Read the next batch of messages.
 		c.messages = c.messages[:batchSize]
@@ -189,21 +193,16 @@ func (c *oobConn) ReadPacket() (receivedPacket, error) {
 			case msgTypeIPTOS:
 				p.ecn = protocol.ECN(body[0] & ecnMask)
 			case ipv4PKTINFO:
-				// struct in_pktinfo {
-				// 	unsigned int   ipi_ifindex;  /* Interface index */
-				// 	struct in_addr ipi_spec_dst; /* Local address */
-				// 	struct in_addr ipi_addr;     /* Header Destination
-				// 									address */
-				// };
-				var ip [4]byte
-				if len(body) == 12 {
-					copy(ip[:], body[8:12])
-					p.info.ifIndex = binary.LittleEndian.Uint32(body)
-				} else if len(body) == 4 {
-					// FreeBSD
-					copy(ip[:], body)
+				ip, ifIndex, ok := parseIPv4PktInfo(body)
+				if ok {
+					p.info.addr = ip
+					p.info.ifIndex = ifIndex
+				} else {
+					invalidCmsgOnceV4.Do(func() {
+						log.Printf("Received invalid IPv4 packet info control message: %+x. "+
+							"This should never occur, please open a new issue and include details about the architecture.", body)
+					})
 				}
-				p.info.addr = netip.AddrFrom4(ip)
 			}
 		}
 		if hdr.Level == unix.IPPROTO_IPV6 {
@@ -216,10 +215,13 @@ func (c *oobConn) ReadPacket() (receivedPacket, error) {
 				// 	unsigned int    ipi6_ifindex; /* send/recv interface index */
 				// };
 				if len(body) == 20 {
-					var ip [16]byte
-					copy(ip[:], body[:16])
-					p.info.addr = netip.AddrFrom16(ip)
+					p.info.addr = netip.AddrFrom16(*(*[16]byte)(body[:16]))
 					p.info.ifIndex = binary.LittleEndian.Uint32(body[16:])
+				} else {
+					invalidCmsgOnceV6.Do(func() {
+						log.Printf("Received invalid IPv6 packet info control message: %+x. "+
+							"This should never occur, please open a new issue and include details about the architecture.", body)
+					})
 				}
 			}
 		}