c - Add data to packet of a specific protocol -

-

i'm implementing new protocol called xor. first packets created in user space , sent network. after packet arrive other node in network. need create module intercept every module sent , add header or data. create module put data packet don't have success.

i try things when activate module packets dropped. module doing:

struct xorhdr {     int in;     int out; };  static unsigned int asnfwd_hook(const struct nf_hook_ops *ops, struct sk_buff *skb, const struct net_device *in, const struct net_device *out, int (*okfn)(struct sk_buff *)) {     struct iphdr *iph;     struct asnfwd_opt *opt;     __be32 addr = 0;     struct tcphdr *th;     struct udphdr *uh;      /* sanity check */     if (!skb)         goto accept;      /* recover ipv4 header */     iph = ip_hdr(skb);     if (!iph)         goto accept;      if (iph->protocol == 17) {         uh = (struct udphdr *) skb_transport_header(skb);         if ((unsigned int) ntohs(uh->source) == xor_port && (unsigned int) ntohs(uh->dest) == xor_port) {             printk("\n****************************\n");             printk("hook %s\n", (in ? "pre-routing" : "local-out"));             printk("(ogirinal) %pi4 %pi4.\n", &iph->saddr, &iph->daddr);             printk(kern_info "free:%d", skb_headroom(skb));              if (in) {                 struct xorhdr *ptr;                  if (skb->tail + sizeof(struct xorhdr) < skb->end) {                     unsigned char* tail_ptr = skb_tail_pointer(skb);                     ptr = (struct xorhdr *)(tail_ptr);                     printk(kern_info "cbin:%d\n", ptr->in);                     printk(kern_info "cbout:%d\n", ptr->out);                 }              } else {                 if (skb_headroom(skb) > sizeof(struct xorhdr)) {                     struct xorhdr *xorh;                     xorh = kmalloc(sizeof(struct xorhdr), gfp_atomic);                     unsigned char *new_data;                      new_data = skb_tail_pointer(skb);                     if (skb->tail + sizeof(struct xorhdr) < skb->end) {                         xorh->in = 6;                         xorh->out = 5;                         printk(kern_info "cbin:%d\n", xorh->in);                         printk(kern_info "cbout:%d\n", xorh->out);                         skb->tail += sizeof(struct xorhdr);                         skb->len += sizeof(struct xorhdr);                         memcpy(new_data, xorh, sizeof(struct xorhdr));                     }                      kfree(xorh);                      // update ip header pointer                      iph = ip_hdr(skb);                      // calculate udp checksum                     uh = udp_hdr(skb);                     uh->check = 0;                     uh->check = csum_tcpudp_magic(iph->saddr, iph->daddr, ip_payload_len(iph), ipproto_udp, csum_partial(uh, ip_payload_len(iph), skb->csum));                     skb->ip_summed = checksum_none;                      // calculate ip checksum                      ip_send_check (iph);                  }             }             printk("\n****************************\n\n");         }       }      accept:         return nf_accept; }

what i'm doing wrong?

i solved problem moving skb->tail original position doing this: skb->tail -= sizeof(struct xorhdr);. when receive package in other side use data put, , return skb->tail original position.

struct xorhdr {     int in;     int out; };  static unsigned int asnfwd_hook(const struct nf_hook_ops *ops, struct sk_buff *skb, const struct net_device *in, const struct net_device *out, int (*okfn)(struct sk_buff *)) {     struct iphdr *iph;     struct asnfwd_opt *opt;     __be32 addr = 0;     struct tcphdr *th;     struct udphdr *uh;      /* sanity check */     if (!skb)         goto accept;      /* recover ipv4 header */     iph = ip_hdr(skb);     if (!iph)         goto accept;      if (iph->protocol == 17) {         uh = (struct udphdr *) skb_transport_header(skb);         if ((unsigned int) ntohs(uh->source) == xor_port && (unsigned int) ntohs(uh->dest) == xor_port) {             printk("\n****************************\n");             printk("hook %s\n", (in ? "pre-routing" : "local-out"));             printk("(ogirinal) %pi4 %pi4.\n", &iph->saddr, &iph->daddr);             printk(kern_info "free:%d", skb_headroom(skb));              if (in) {                 struct xorhdr *ptr;                  if (skb->tail + sizeof(struct xorhdr) < skb->end) {                     unsigned char* tail_ptr = skb_tail_pointer(skb);                     ptr = (struct xorhdr *)(tail_ptr);                     printk(kern_info "cbin:%d\n", ptr->in);                     printk(kern_info "cbout:%d\n", ptr->out);                     skb->tail -= sizeof(struct xorhdr);                      // update ip header pointer                      iph = ip_hdr(skb);                      // calculate udp checksum                     uh = udp_hdr(skb);                     uh->check = 0;                     uh->check = csum_tcpudp_magic(iph->saddr, iph->daddr, ip_payload_len(iph), ipproto_udp, csum_partial(uh, ip_payload_len(iph), skb->csum));                     skb->ip_summed = checksum_none;                      // calculate ip checksum                      ip_send_check (iph);                 }              } else {                 if (skb_headroom(skb) > sizeof(struct xorhdr)) {                     struct xorhdr *xorh;                     xorh = kmalloc(sizeof(struct xorhdr), gfp_atomic);                     unsigned char *new_data;                      new_data = skb_tail_pointer(skb);                     if (skb->tail + sizeof(struct xorhdr) < skb->end) {                         xorh->in = 6;                         xorh->out = 5;                         printk(kern_info "cbin:%d\n", xorh->in);                         printk(kern_info "cbout:%d\n", xorh->out);                         skb->tail += sizeof(struct xorhdr);                         skb->len += sizeof(struct xorhdr);                         memcpy(new_data, xorh, sizeof(struct xorhdr));                     }                      kfree(xorh);                      // update ip header pointer                      iph = ip_hdr(skb);                      // calculate udp checksum                     uh = udp_hdr(skb);                     uh->check = 0;                     uh->check = csum_tcpudp_magic(iph->saddr, iph->daddr, ip_payload_len(iph), ipproto_udp, csum_partial(uh, ip_payload_len(iph), skb->csum));                     skb->ip_summed = checksum_none;                      // calculate ip checksum                      ip_send_check (iph);                  }             }             printk("\n****************************\n\n");         }       }      accept:         return nf_accept; }

Comments

Post a Comment

Popular posts from this blog

java - Static nested class instance -

-
this question has answer here: java inner class , static nested class 23 answers i came across in java, know static nested class why create instance of 'static'. isn't whole idea of 'static' use without instance? understand concept of inner classes, why (and frankly how possible to) create 'instance' of 'static' member @ ? why this: 1- outerclass.staticnestedclass nestedobject = new outerclass.staticnestedclass(); 2- nestedobject.anestedclassmethod(); and not this: 1- outerclass outerinstance=new outerclass(); 2- outerinstance.staticnestedclass.anestedclassmethod(); use on inner classes, keyword static indicates can access inner class without instance of outer class. for example: public class outer { public static class inner { /* code here. */ } } with construction, can create instance of inn
Read more

c# - Bluetooth LE CanUpdate Characteristic property -

-
i building xamarin.forms cross platform mobile app, uses monkey.robotics bluetoth low energy functionality. connecting mbed based implimentation of custom gatt service . in xamarin c#, triggers characteristic. canupdate property in monkey.robotics? this standard example c# based on: if (characteristic.canupdate) { characteristic.valueupdated += (s, e) => { debug.writeline("characteristic.valueupdated"); device.begininvokeonmainthread( () => { updatedisplay(characteristic); }); isbusy = false; // spin until first result received }; isbusy = true; characteristic.startupdates(); } this has been working, since changed own custom gatt service connecting to, canupdate property false. property , how triggered? me debugging gatt service code. thanks monkey.robotics open sour
Read more

JavaScript - Replace variable from string in all occurrences -

-
ok, know if have character '-' , want remove in places in string javascript, ... someword = someword.replace(/-/g, ''); but, when applying array of characters, s not working ... const badchars = ('\/:*?"<>|').split(''); let filename = title.replace(/ /g, '-').tolocalelowercase(); (let item = 0; item < badchars.length; item++) { // below not work global '/ /g' filename = filename.replace(/badchars[item]/g, ''); } any ideas? /badchars[item]/g looks badchars , literally, followed i , t , e , or m . if you're trying use character badchars[item] , you'll need use regexp constructor, , you'll need escape regex-specific characters. escaping regular expression has been well-covered . using that: filename = filename.replace(new regexp(regexp.quote(badchars[item]), 'g'), ''); but , don't want that. want character class: let filename = title.replac
Read more