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Annotation of researchv10no/sys/inet/udp_output.c, revision 1.1

1.1     ! root        1: /*     udp_output.c    6.1     83/07/29        */
        !             2: 
        !             3: #include "sys/param.h"
        !             4: #include "sys/stream.h"
        !             5: 
        !             6: #include "sys/inet/in.h"
        !             7: #include "sys/inet/ip.h"
        !             8: #include "sys/inet/ip_var.h"
        !             9: #include "sys/inet/udp.h"
        !            10: #include "sys/inet/udp_var.h"
        !            11: 
        !            12: #define        IPPROTO_UDP     17
        !            13: #define        UDP_DATA_LEN    (1500-sizeof(struct udpiphdr))
        !            14: 
        !            15: /*
        !            16:  * send out list data,
        !            17:  * as a UDP packet
        !            18:  * allocate, prepend, and fill in UDP headers here
        !            19:  */
        !            20: udp_output(data, udp)
        !            21: register struct block *data;
        !            22: register struct udp *udp;
        !            23: {
        !            24:        register struct block *head;
        !            25:        register struct udpiphdr *ui;
        !            26:        register int len;
        !            27: 
        !            28:        len = bp_len(data);
        !            29:        if ((head = allocb(sizeof(struct udpiphdr))) == NULL) {
        !            30:                bp_free(data);
        !            31:                return;
        !            32:        }
        !            33: if (head == data) panic("udp_output");
        !            34:        head->wptr += sizeof(struct udpiphdr);
        !            35:        head->next = data;
        !            36:        /*
        !            37:         * Fill in block with extended UDP header
        !            38:         * and addresses and length put into network format.
        !            39:         */
        !            40:        ui = (struct udpiphdr *)head->rptr;
        !            41:        ui->ui_next = 0;
        !            42:        ui->ui_bp = 0;
        !            43:        ui->ui_x1 = 0;
        !            44:        ui->ui_pr = IPPROTO_UDP;
        !            45:        ui->ui_len = (u_short)len + sizeof (struct udphdr);
        !            46:        ui->ui_len = htons((u_short)(ui->ui_len));
        !            47:        ui->ui_src = htonl(udp->src);
        !            48:        ui->ui_dst = htonl(udp->dst);
        !            49:        ui->ui_sport = htons(udp->sport);
        !            50:        ui->ui_dport = htons(udp->dport);
        !            51:        ui->ui_ulen = ui->ui_len;
        !            52: 
        !            53:        /* Stuff checksum and output datagram. */
        !            54:        ui->ui_sum = 0;
        !            55:        if ((ui->ui_sum = in_cksum(head, sizeof(struct udpiphdr)+len)) == 0)
        !            56:                ui->ui_sum = -1;
        !            57: 
        !            58: 
        !            59:        /* Put length and timeout time into the `real' ip header. */
        !            60:        ((struct ip *)ui)->ip_len = sizeof(struct udpiphdr)+len;
        !            61:        ((struct ip *)ui)->ip_ttl = MAXTTL;
        !            62: 
        !            63:        /* Ip expects internet addresses in host order. */
        !            64:        ui->ui_src = ntohl(ui->ui_src);
        !            65:        ui->ui_dst = ntohl(ui->ui_dst);
        !            66:        udp_ldout(head);
        !            67: }

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