```c
static int nfc_llcp_setsockopt(struct socket *sock, int level, int optname,
			       sockptr_t optval, unsigned int optlen)
{
	struct nfc_llcp_sock *nfc_llcp_sk = sock->sk;
	int ret = 0;

	/* Check for invalid level or optname */
	if (level != SOL_SOCKET) {
		return -EINVAL;
	}

	switch (optname) {
	case SO_SNDBUF:
		/* Handle SO_SNDBUF option */
		if (optlen != sizeof(int)) {
			ret = -EINVAL;
			break;
		}
		nfc_llcp_sk->sndbuf = *(int *)optval;
		break;
	case SO_RCVBUF:
		/* Handle SO_RCVBUF option */
		if (optlen != sizeof(int)) {
			ret = -EINVAL;
			break;
		}
		nfc_llcp_sk->rcvbuf = *(int *)optval;
		break;
	case SO_LINGER:
		/* Handle SO_LINGER option */
		if (optlen != sizeof(struct linger)) {
			ret = -EINVAL;
			break;
		}
		nfc_llcp_sk->linger = *(struct linger *)optval;
		break;
	case SO_KEEPALIVE:
		/* Handle SO_KEEPALIVE option */
		if (optlen != sizeof(int)) {
			ret = -EINVAL;
			break;
		}
		nfc_llcp_sk->keepalive = *(int *)optval;
		break;
	default:
		ret = -EINVAL;
		break;
	}

	return ret;
}
```

**Possible Code Completions:**

**1. Handling SO_SNDTIMEO and SO_RCVTIMEO:**

```c
	case SO_SNDTIMEO:
		/* Handle SO_SNDTIMEO option */
		if (optlen != sizeof(struct timeval)) {
			ret = -EINVAL;
			break;
		}
		nfc_llcp_sk->sndtimeo = *(struct timeval *)optval;
		break;
	case SO_RCVTIMEO:
		/* Handle SO_RCVTIMEO option */
		if (optlen != sizeof(struct timeval)) {
			ret = -EINVAL;
			break;
		}
		nfc_llcp_sk->rcvtimeo = *(struct timeval *)optval;
		break;
```

**2. Handling SO_REUSEADDR:**

```c
	case SO_REUSEADDR:
		/* Handle SO_REUSEADDR option */
		if (optlen != sizeof(int)) {
			ret = -EINVAL;
			break;
		}
		nfc_llcp_sk->reuseaddr = *(int *)optval;
		break;
```

**3. Handling SO_BROADCAST:**

```c
	case SO_BROADCAST:
		/* Handle SO_BROADCAST option */
		if (optlen != sizeof(int)) {
			ret = -EINVAL;
			break;
		}
		nfc_llcp_sk->broadcast = *(int *)optval;
		break;
```

**4. Handling SO_DONTROUTE:**

```c
	case SO_DONTROUTE:
		/* Handle SO_DONTROUTE option */
		if (optlen != sizeof(int)) {
			ret = -EINVAL;
			break;
		}
		nfc_llcp_sk->dontroute = *(int *)optval;
		break;
```

**5. Handling custom options specific to NFC LLCP:**

```c
	case NFC_LLCP_OPT_MTU:
		/* Handle NFC_LLCP_OPT_MTU option */
		if (optlen != sizeof(int)) {
			ret = -EINVAL;
			break;
		}
		nfc_llcp_sk->mtu = *(int *)optval;
		break;
```

**Note:** The specific options and their implementations will depend on the requirements of your NFC LLCP implementation. The provided examples are just suggestions and should be adapted accordingly. 
